<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with Wdesk from Workiva-->
<!--Copyright 2022 Workiva-->
<!--r:db8566d6-d837-477c-9a31-bbc9440b078b,g:f26e0c5e-fe2b-430d-bf8e-5f9082b5f746-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member"/>
  <link:roleRef roleURI="http://eosenergystorage.com/role/Cover" xlink:type="simple" xlink:href="eose-20220930.xsd#Cover"/>
  <link:definitionLink xlink:role="http://eosenergystorage.com/role/Cover" xlink:type="extended" id="i66a1124c5949434bbb9dc3be3e7005c5_Cover">
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentInformationLineItems_bc66b74b-1926-4250-97d1-6a8cfe361d87" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_DocumentInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentType_5328d377-a73e-49c1-96dd-006a905a4f9c" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_DocumentType"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_bc66b74b-1926-4250-97d1-6a8cfe361d87" xlink:to="loc_dei_DocumentType_5328d377-a73e-49c1-96dd-006a905a4f9c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentQuarterlyReport_3b49737b-fd57-4526-acd3-e2a93f422b25" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_DocumentQuarterlyReport"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_bc66b74b-1926-4250-97d1-6a8cfe361d87" xlink:to="loc_dei_DocumentQuarterlyReport_3b49737b-fd57-4526-acd3-e2a93f422b25" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentPeriodEndDate_fa0ac542-c3c7-45e5-a61d-10b75b177393" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_DocumentPeriodEndDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_bc66b74b-1926-4250-97d1-6a8cfe361d87" xlink:to="loc_dei_DocumentPeriodEndDate_fa0ac542-c3c7-45e5-a61d-10b75b177393" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentTransitionReport_714e02f6-c6b7-4cb0-b1ed-49372fdb49cb" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_DocumentTransitionReport"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_bc66b74b-1926-4250-97d1-6a8cfe361d87" xlink:to="loc_dei_DocumentTransitionReport_714e02f6-c6b7-4cb0-b1ed-49372fdb49cb" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFileNumber_873049d8-da52-4803-8046-bcba23df0f6e" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityFileNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_bc66b74b-1926-4250-97d1-6a8cfe361d87" xlink:to="loc_dei_EntityFileNumber_873049d8-da52-4803-8046-bcba23df0f6e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityRegistrantName_1618dc52-d8e8-4d8c-a3cd-be05026d6ca9" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityRegistrantName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_bc66b74b-1926-4250-97d1-6a8cfe361d87" xlink:to="loc_dei_EntityRegistrantName_1618dc52-d8e8-4d8c-a3cd-be05026d6ca9" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityIncorporationStateCountryCode_d3bcafc2-a959-42dc-8e46-35e61124392e" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityIncorporationStateCountryCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_bc66b74b-1926-4250-97d1-6a8cfe361d87" xlink:to="loc_dei_EntityIncorporationStateCountryCode_d3bcafc2-a959-42dc-8e46-35e61124392e" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityTaxIdentificationNumber_af719651-60ec-4706-bbe5-115d54206abc" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityTaxIdentificationNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_bc66b74b-1926-4250-97d1-6a8cfe361d87" xlink:to="loc_dei_EntityTaxIdentificationNumber_af719651-60ec-4706-bbe5-115d54206abc" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine1_0c345c1d-9c78-4024-916e-1b6eba7ec78b" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityAddressAddressLine1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_bc66b74b-1926-4250-97d1-6a8cfe361d87" xlink:to="loc_dei_EntityAddressAddressLine1_0c345c1d-9c78-4024-916e-1b6eba7ec78b" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressCityOrTown_25577ead-c1d2-4206-9f75-4705476eaaca" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityAddressCityOrTown"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_bc66b74b-1926-4250-97d1-6a8cfe361d87" xlink:to="loc_dei_EntityAddressCityOrTown_25577ead-c1d2-4206-9f75-4705476eaaca" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressStateOrProvince_7f3a4b27-01b0-41a5-9a4f-a0216189a423" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityAddressStateOrProvince"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_bc66b74b-1926-4250-97d1-6a8cfe361d87" xlink:to="loc_dei_EntityAddressStateOrProvince_7f3a4b27-01b0-41a5-9a4f-a0216189a423" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressPostalZipCode_0610ba7a-b4bc-4757-9376-fe3ef0fadd25" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityAddressPostalZipCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_bc66b74b-1926-4250-97d1-6a8cfe361d87" xlink:to="loc_dei_EntityAddressPostalZipCode_0610ba7a-b4bc-4757-9376-fe3ef0fadd25" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CityAreaCode_173826a8-061f-4db7-af10-aa3b5c8bef99" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_CityAreaCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_bc66b74b-1926-4250-97d1-6a8cfe361d87" xlink:to="loc_dei_CityAreaCode_173826a8-061f-4db7-af10-aa3b5c8bef99" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LocalPhoneNumber_ace8d192-9e87-4bb7-924c-0b540ad0b2e3" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_LocalPhoneNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_bc66b74b-1926-4250-97d1-6a8cfe361d87" xlink:to="loc_dei_LocalPhoneNumber_ace8d192-9e87-4bb7-924c-0b540ad0b2e3" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_Security12bTitle_ff73889f-0106-4c1d-ad01-f2e3b2a1abab" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_Security12bTitle"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_bc66b74b-1926-4250-97d1-6a8cfe361d87" xlink:to="loc_dei_Security12bTitle_ff73889f-0106-4c1d-ad01-f2e3b2a1abab" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_TradingSymbol_6f696168-c8e6-4389-8317-6652d4602ffa" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_TradingSymbol"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_bc66b74b-1926-4250-97d1-6a8cfe361d87" xlink:to="loc_dei_TradingSymbol_6f696168-c8e6-4389-8317-6652d4602ffa" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_SecurityExchangeName_7fb6bf47-17bd-4ed5-89ef-e780cf3dfbf6" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_SecurityExchangeName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_bc66b74b-1926-4250-97d1-6a8cfe361d87" xlink:to="loc_dei_SecurityExchangeName_7fb6bf47-17bd-4ed5-89ef-e780cf3dfbf6" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCurrentReportingStatus_e2c34151-68f4-4280-9260-0b119ca59a53" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityCurrentReportingStatus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_bc66b74b-1926-4250-97d1-6a8cfe361d87" xlink:to="loc_dei_EntityCurrentReportingStatus_e2c34151-68f4-4280-9260-0b119ca59a53" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityInteractiveDataCurrent_43e5f102-d603-4ee8-ad01-e34b8caacb8c" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityInteractiveDataCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_bc66b74b-1926-4250-97d1-6a8cfe361d87" xlink:to="loc_dei_EntityInteractiveDataCurrent_43e5f102-d603-4ee8-ad01-e34b8caacb8c" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFilerCategory_539cc087-1c23-4695-822b-dd277956d02d" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityFilerCategory"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_bc66b74b-1926-4250-97d1-6a8cfe361d87" xlink:to="loc_dei_EntityFilerCategory_539cc087-1c23-4695-822b-dd277956d02d" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntitySmallBusiness_832f3a2a-af5a-489b-9613-d7417898968e" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntitySmallBusiness"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_bc66b74b-1926-4250-97d1-6a8cfe361d87" xlink:to="loc_dei_EntitySmallBusiness_832f3a2a-af5a-489b-9613-d7417898968e" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityEmergingGrowthCompany_2ffcd7f2-2044-42cf-949e-ce4c8437feb4" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityEmergingGrowthCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_bc66b74b-1926-4250-97d1-6a8cfe361d87" xlink:to="loc_dei_EntityEmergingGrowthCompany_2ffcd7f2-2044-42cf-949e-ce4c8437feb4" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityShellCompany_7b06e41b-7eca-441e-bfb5-f6be3ca1985d" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityShellCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_bc66b74b-1926-4250-97d1-6a8cfe361d87" xlink:to="loc_dei_EntityShellCompany_7b06e41b-7eca-441e-bfb5-f6be3ca1985d" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCommonStockSharesOutstanding_fe85d2d2-9484-436e-b204-bd76ffb64aff" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityCommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_bc66b74b-1926-4250-97d1-6a8cfe361d87" xlink:to="loc_dei_EntityCommonStockSharesOutstanding_fe85d2d2-9484-436e-b204-bd76ffb64aff" xlink:type="arc" order="23"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCentralIndexKey_d3b59d93-ed99-4b45-8156-a7761200de54" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityCentralIndexKey"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_bc66b74b-1926-4250-97d1-6a8cfe361d87" xlink:to="loc_dei_EntityCentralIndexKey_d3b59d93-ed99-4b45-8156-a7761200de54" xlink:type="arc" order="24"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_AmendmentFlag_35ae7d6b-42a3-4ce8-b5e6-cc158160624f" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_AmendmentFlag"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_bc66b74b-1926-4250-97d1-6a8cfe361d87" xlink:to="loc_dei_AmendmentFlag_35ae7d6b-42a3-4ce8-b5e6-cc158160624f" xlink:type="arc" order="25"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CurrentFiscalYearEndDate_a41b0dce-e31d-4f8d-8570-c392c64720a0" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_CurrentFiscalYearEndDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_bc66b74b-1926-4250-97d1-6a8cfe361d87" xlink:to="loc_dei_CurrentFiscalYearEndDate_a41b0dce-e31d-4f8d-8570-c392c64720a0" xlink:type="arc" order="26"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentFiscalPeriodFocus_00ecdfef-a238-4c8d-aee4-27b22d2aecf2" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_DocumentFiscalPeriodFocus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_bc66b74b-1926-4250-97d1-6a8cfe361d87" xlink:to="loc_dei_DocumentFiscalPeriodFocus_00ecdfef-a238-4c8d-aee4-27b22d2aecf2" xlink:type="arc" order="27"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentFiscalYearFocus_92c45fb8-9c33-472d-8ce1-0cc0fd99f3aa" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_DocumentFiscalYearFocus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_bc66b74b-1926-4250-97d1-6a8cfe361d87" xlink:to="loc_dei_DocumentFiscalYearFocus_92c45fb8-9c33-472d-8ce1-0cc0fd99f3aa" xlink:type="arc" order="28"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentInformationTable_347eb0ec-b3a1-4001-a060-f6ce7e5993bc" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_DocumentInformationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_dei_DocumentInformationLineItems_bc66b74b-1926-4250-97d1-6a8cfe361d87" xlink:to="loc_dei_DocumentInformationTable_347eb0ec-b3a1-4001-a060-f6ce7e5993bc" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_af7b75c5-e2a6-43f7-81d3-7206376cd35a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_DocumentInformationTable_347eb0ec-b3a1-4001-a060-f6ce7e5993bc" xlink:to="loc_us-gaap_StatementClassOfStockAxis_af7b75c5-e2a6-43f7-81d3-7206376cd35a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_af7b75c5-e2a6-43f7-81d3-7206376cd35a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_af7b75c5-e2a6-43f7-81d3-7206376cd35a" xlink:to="loc_us-gaap_ClassOfStockDomain_af7b75c5-e2a6-43f7-81d3-7206376cd35a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_27b8847f-1876-44b0-910a-49d0d06f9bf8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_af7b75c5-e2a6-43f7-81d3-7206376cd35a" xlink:to="loc_us-gaap_ClassOfStockDomain_27b8847f-1876-44b0-910a-49d0d06f9bf8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_46ac1c8d-066a-4010-8ccd-9075cd8e1d8e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_27b8847f-1876-44b0-910a-49d0d06f9bf8" xlink:to="loc_us-gaap_CommonStockMember_46ac1c8d-066a-4010-8ccd-9075cd8e1d8e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WarrantMember_7cbb5ea0-1b75-458e-871f-e48f8bde84a9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_WarrantMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_27b8847f-1876-44b0-910a-49d0d06f9bf8" xlink:to="loc_us-gaap_WarrantMember_7cbb5ea0-1b75-458e-871f-e48f8bde84a9" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://eosenergystorage.com/role/UNAUDITEDCONDENSEDCONSOLIDATEDSTATEMENTSOFSHAREHOLDERSDEFICITEQUITY" xlink:type="simple" xlink:href="eose-20220930.xsd#UNAUDITEDCONDENSEDCONSOLIDATEDSTATEMENTSOFSHAREHOLDERSDEFICITEQUITY"/>
  <link:definitionLink xlink:role="http://eosenergystorage.com/role/UNAUDITEDCONDENSEDCONSOLIDATEDSTATEMENTSOFSHAREHOLDERSDEFICITEQUITY" xlink:type="extended" id="i148659fd8ac04c839cc9f315e5090f99_UNAUDITEDCONDENSEDCONSOLIDATEDSTATEMENTSOFSHAREHOLDERSDEFICITEQUITY">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_e3cea6f3-fe5e-4910-be37-bdaf0cd0c3c7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_3758f9fd-797f-435f-9691-4b849dfa07d3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_e3cea6f3-fe5e-4910-be37-bdaf0cd0c3c7" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_3758f9fd-797f-435f-9691-4b849dfa07d3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_2dc7c26c-96cb-400b-b9ee-18c069246c9f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_3758f9fd-797f-435f-9691-4b849dfa07d3" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_2dc7c26c-96cb-400b-b9ee-18c069246c9f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_3a2448bd-478e-40cf-8c57-3d2bf6a0e7f2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_3758f9fd-797f-435f-9691-4b849dfa07d3" xlink:to="loc_us-gaap_StockholdersEquity_3a2448bd-478e-40cf-8c57-3d2bf6a0e7f2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_3d4d60ef-5f45-4405-bc29-1d6d2ea87a9b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_3758f9fd-797f-435f-9691-4b849dfa07d3" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_3d4d60ef-5f45-4405-bc29-1d6d2ea87a9b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesAcquisitions_59452206-d89d-47cd-9a49-84abc53581eb" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockIssuedDuringPeriodSharesAcquisitions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_3758f9fd-797f-435f-9691-4b849dfa07d3" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesAcquisitions_59452206-d89d-47cd-9a49-84abc53581eb" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_StockIssuedDuringPeriodSharesContingentlyIssuableStock_6b7958ac-e805-42b0-bdc7-22b07caeee2d" xlink:href="eose-20220930.xsd#eose_StockIssuedDuringPeriodSharesContingentlyIssuableStock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_3758f9fd-797f-435f-9691-4b849dfa07d3" xlink:to="loc_eose_StockIssuedDuringPeriodSharesContingentlyIssuableStock_6b7958ac-e805-42b0-bdc7-22b07caeee2d" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_StockIssuedDuringPeriodValueContingentlyIssuableStock_5b35b3fe-10c4-4b32-94c9-7a1b0d809ca3" xlink:href="eose-20220930.xsd#eose_StockIssuedDuringPeriodValueContingentlyIssuableStock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_3758f9fd-797f-435f-9691-4b849dfa07d3" xlink:to="loc_eose_StockIssuedDuringPeriodValueContingentlyIssuableStock_5b35b3fe-10c4-4b32-94c9-7a1b0d809ca3" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_032418ad-7997-4bcd-996c-aa7793378f27" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_3758f9fd-797f-435f-9691-4b849dfa07d3" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_032418ad-7997-4bcd-996c-aa7793378f27" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_2fdaf6f1-aa14-4efc-ae7a-d97a5df555d2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_3758f9fd-797f-435f-9691-4b849dfa07d3" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_2fdaf6f1-aa14-4efc-ae7a-d97a5df555d2" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_StockIssuedDuringPeriodSharesWarrantsExercised_5bccb15d-10eb-4b29-bf90-7ac720b60040" xlink:href="eose-20220930.xsd#eose_StockIssuedDuringPeriodSharesWarrantsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_3758f9fd-797f-435f-9691-4b849dfa07d3" xlink:to="loc_eose_StockIssuedDuringPeriodSharesWarrantsExercised_5bccb15d-10eb-4b29-bf90-7ac720b60040" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_AdjustmentsToAdditionalPaidInCapitalWarrantExercised_afaa40a2-272c-4e53-b135-6739a437c000" xlink:href="eose-20220930.xsd#eose_AdjustmentsToAdditionalPaidInCapitalWarrantExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_3758f9fd-797f-435f-9691-4b849dfa07d3" xlink:to="loc_eose_AdjustmentsToAdditionalPaidInCapitalWarrantExercised_afaa40a2-272c-4e53-b135-6739a437c000" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardGross_0f95da68-9839-4dd6-be71-edfbcd2b4b6d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_3758f9fd-797f-435f-9691-4b849dfa07d3" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardGross_0f95da68-9839-4dd6-be71-edfbcd2b4b6d" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation_d6772454-d39a-471c-9e7b-a01fb0841d01" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_3758f9fd-797f-435f-9691-4b849dfa07d3" xlink:to="loc_us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation_d6772454-d39a-471c-9e7b-a01fb0841d01" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation_92a7666e-f7c9-4190-a5d2-2e8dac8043fa" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_3758f9fd-797f-435f-9691-4b849dfa07d3" xlink:to="loc_us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation_92a7666e-f7c9-4190-a5d2-2e8dac8043fa" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities_9cf9feeb-e253-4981-a4ea-23b7b9a3d747" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_3758f9fd-797f-435f-9691-4b849dfa07d3" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities_9cf9feeb-e253-4981-a4ea-23b7b9a3d747" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueConversionOfConvertibleSecurities_9599ac5e-62ec-42ed-b0b1-dff3464ecae9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockIssuedDuringPeriodValueConversionOfConvertibleSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_3758f9fd-797f-435f-9691-4b849dfa07d3" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueConversionOfConvertibleSecurities_9599ac5e-62ec-42ed-b0b1-dff3464ecae9" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_0354212c-7371-43d3-bb81-086cef6dbe72" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockIssuedDuringPeriodSharesNewIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_3758f9fd-797f-435f-9691-4b849dfa07d3" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_0354212c-7371-43d3-bb81-086cef6dbe72" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_12fda4dd-890e-4743-b22e-1bf9de7249f0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockIssuedDuringPeriodValueNewIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_3758f9fd-797f-435f-9691-4b849dfa07d3" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_12fda4dd-890e-4743-b22e-1bf9de7249f0" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_StockIssuedDuringPeriodSharesStandbyEquityPurchaseAgreement_8cae6cff-2290-4277-8eef-1c30868c6b03" xlink:href="eose-20220930.xsd#eose_StockIssuedDuringPeriodSharesStandbyEquityPurchaseAgreement"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_3758f9fd-797f-435f-9691-4b849dfa07d3" xlink:to="loc_eose_StockIssuedDuringPeriodSharesStandbyEquityPurchaseAgreement_8cae6cff-2290-4277-8eef-1c30868c6b03" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_StockIssuedDuringPeriodValueStandbyEquityPurchaseAgreement_25203871-9ef2-4840-ac05-ee466c8e9bca" xlink:href="eose-20220930.xsd#eose_StockIssuedDuringPeriodValueStandbyEquityPurchaseAgreement"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_3758f9fd-797f-435f-9691-4b849dfa07d3" xlink:to="loc_eose_StockIssuedDuringPeriodValueStandbyEquityPurchaseAgreement_25203871-9ef2-4840-ac05-ee466c8e9bca" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_StockIssuedDuringPeriodSharesCommitmentFee_6835b480-576b-4bf3-b096-b68035553d1c" xlink:href="eose-20220930.xsd#eose_StockIssuedDuringPeriodSharesCommitmentFee"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_3758f9fd-797f-435f-9691-4b849dfa07d3" xlink:to="loc_eose_StockIssuedDuringPeriodSharesCommitmentFee_6835b480-576b-4bf3-b096-b68035553d1c" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_StockIssuedDuringPeriodValueCommitmentFee_9f746a34-ca54-4095-bfdf-707426131e35" xlink:href="eose-20220930.xsd#eose_StockIssuedDuringPeriodValueCommitmentFee"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_3758f9fd-797f-435f-9691-4b849dfa07d3" xlink:to="loc_eose_StockIssuedDuringPeriodValueCommitmentFee_9f746a34-ca54-4095-bfdf-707426131e35" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationAdjustmentNetOfTaxPortionAttributableToParent_e59a5a2d-d1d9-472e-a97f-549a3ff437e2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationAdjustmentNetOfTaxPortionAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_3758f9fd-797f-435f-9691-4b849dfa07d3" xlink:to="loc_us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationAdjustmentNetOfTaxPortionAttributableToParent_e59a5a2d-d1d9-472e-a97f-549a3ff437e2" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_7840b5dc-f13f-4d4f-bec5-9692a4c58df4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_3758f9fd-797f-435f-9691-4b849dfa07d3" xlink:to="loc_us-gaap_NetIncomeLoss_7840b5dc-f13f-4d4f-bec5-9692a4c58df4" xlink:type="arc" order="23"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_8d8e6c54-c40b-4565-855f-767879414600" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_48284e83-b028-48ec-b894-7b39b2f805cd" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockholdersEquity"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_b743d7df-3cb6-4b60-86da-b795756d1a74" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_e3cea6f3-fe5e-4910-be37-bdaf0cd0c3c7" xlink:to="loc_us-gaap_StatementTable_b743d7df-3cb6-4b60-86da-b795756d1a74" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_6741b7f1-cb9c-4802-ab2e-94cef2a44f0d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_b743d7df-3cb6-4b60-86da-b795756d1a74" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_6741b7f1-cb9c-4802-ab2e-94cef2a44f0d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_6741b7f1-cb9c-4802-ab2e-94cef2a44f0d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_6741b7f1-cb9c-4802-ab2e-94cef2a44f0d" xlink:to="loc_us-gaap_EquityComponentDomain_6741b7f1-cb9c-4802-ab2e-94cef2a44f0d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_931dc18f-de83-40d0-afa8-b6fc785b4b6b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_6741b7f1-cb9c-4802-ab2e-94cef2a44f0d" xlink:to="loc_us-gaap_EquityComponentDomain_931dc18f-de83-40d0-afa8-b6fc785b4b6b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_8d7cc5ea-dc72-473d-a4ba-64bf760927a5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_931dc18f-de83-40d0-afa8-b6fc785b4b6b" xlink:to="loc_us-gaap_CommonStockMember_8d7cc5ea-dc72-473d-a4ba-64bf760927a5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_7e4699ee-a392-4c18-a2ac-abb33c9da9f9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_931dc18f-de83-40d0-afa8-b6fc785b4b6b" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_7e4699ee-a392-4c18-a2ac-abb33c9da9f9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_ContingentlyIssuableCommonStockMember_e024b729-9f27-4240-9646-f3ef025dabbf" xlink:href="eose-20220930.xsd#eose_ContingentlyIssuableCommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_931dc18f-de83-40d0-afa8-b6fc785b4b6b" xlink:to="loc_eose_ContingentlyIssuableCommonStockMember_e024b729-9f27-4240-9646-f3ef025dabbf" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_00671bf7-c54b-4af5-a0cd-ea9725e78239" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_931dc18f-de83-40d0-afa8-b6fc785b4b6b" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_00671bf7-c54b-4af5-a0cd-ea9725e78239" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_9fc454a9-2c9f-4ce9-b707-2972e6661fac" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_931dc18f-de83-40d0-afa8-b6fc785b4b6b" xlink:to="loc_us-gaap_RetainedEarningsMember_9fc454a9-2c9f-4ce9-b707-2972e6661fac" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://eosenergystorage.com/role/UNAUDITEDCONDENSEDCONSOLIDATEDSTATEMENTSOFCASHFLOWS" xlink:type="simple" xlink:href="eose-20220930.xsd#UNAUDITEDCONDENSEDCONSOLIDATEDSTATEMENTSOFCASHFLOWS"/>
  <link:definitionLink xlink:role="http://eosenergystorage.com/role/UNAUDITEDCONDENSEDCONSOLIDATEDSTATEMENTSOFCASHFLOWS" xlink:type="extended" id="i2f4309d39afc4094aeba369677dcecd8_UNAUDITEDCONDENSEDCONSOLIDATEDSTATEMENTSOFCASHFLOWS">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_54f50675-a302-46d7-8069-b2d6b3dcb179" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_0cc58653-3a02-4c14-a20b-e27f9eb258bd" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_54f50675-a302-46d7-8069-b2d6b3dcb179" xlink:to="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_0cc58653-3a02-4c14-a20b-e27f9eb258bd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_034ada6f-84c2-46de-91d9-5a79f867e72a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_0cc58653-3a02-4c14-a20b-e27f9eb258bd" xlink:to="loc_us-gaap_NetIncomeLoss_034ada6f-84c2-46de-91d9-5a79f867e72a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_376a57b8-7202-4949-8103-b2cbdc6b0293" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_0cc58653-3a02-4c14-a20b-e27f9eb258bd" xlink:to="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_376a57b8-7202-4949-8103-b2cbdc6b0293" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensation_2dba68ea-d113-4786-ac29-250218bf06cc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_376a57b8-7202-4949-8103-b2cbdc6b0293" xlink:to="loc_us-gaap_ShareBasedCompensation_2dba68ea-d113-4786-ac29-250218bf06cc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationDepletionAndAmortization_bae2d78f-793c-4eb7-9fa5-d1ba884ce5d4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DepreciationDepletionAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_376a57b8-7202-4949-8103-b2cbdc6b0293" xlink:to="loc_us-gaap_DepreciationDepletionAndAmortization_bae2d78f-793c-4eb7-9fa5-d1ba884ce5d4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnSaleOfPropertyPlantEquipment_bd1ab570-6526-435f-ab2d-e4e6d532df89" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_GainLossOnSaleOfPropertyPlantEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_376a57b8-7202-4949-8103-b2cbdc6b0293" xlink:to="loc_us-gaap_GainLossOnSaleOfPropertyPlantEquipment_bd1ab570-6526-435f-ab2d-e4e6d532df89" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainsLossesOnExtinguishmentOfDebt_ead7dbfc-917b-4d20-aabc-c1b69c6f9bff" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_GainsLossesOnExtinguishmentOfDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_376a57b8-7202-4949-8103-b2cbdc6b0293" xlink:to="loc_us-gaap_GainsLossesOnExtinguishmentOfDebt_ead7dbfc-917b-4d20-aabc-c1b69c6f9bff" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseRightOfUseAssetAmortizationExpense_94aa2afd-23b0-404b-a4b3-e9f0e99600ab" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OperatingLeaseRightOfUseAssetAmortizationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_376a57b8-7202-4949-8103-b2cbdc6b0293" xlink:to="loc_us-gaap_OperatingLeaseRightOfUseAssetAmortizationExpense_94aa2afd-23b0-404b-a4b3-e9f0e99600ab" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromEquityMethodInvestments_b34b52ed-306f-4390-89eb-016fb41c9463" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncomeLossFromEquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_376a57b8-7202-4949-8103-b2cbdc6b0293" xlink:to="loc_us-gaap_IncomeLossFromEquityMethodInvestments_b34b52ed-306f-4390-89eb-016fb41c9463" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentRealizedGainLossOnDisposal_f562a39c-70fa-4365-a159-ef44a405a31f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityMethodInvestmentRealizedGainLossOnDisposal"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_376a57b8-7202-4949-8103-b2cbdc6b0293" xlink:to="loc_us-gaap_EquityMethodInvestmentRealizedGainLossOnDisposal_f562a39c-70fa-4365-a159-ef44a405a31f" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfFinancingCostsAndDiscounts_94900cfe-ae4c-4a95-8487-8b4a560de8f7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AmortizationOfFinancingCostsAndDiscounts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_376a57b8-7202-4949-8103-b2cbdc6b0293" xlink:to="loc_us-gaap_AmortizationOfFinancingCostsAndDiscounts_94900cfe-ae4c-4a95-8487-8b4a560de8f7" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_AmortizationOfDebtIssuanceCostsAndDiscountsRelatedParty_9008a87d-fe2a-45a6-a152-fc16ccf4f211" xlink:href="eose-20220930.xsd#eose_AmortizationOfDebtIssuanceCostsAndDiscountsRelatedParty"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_376a57b8-7202-4949-8103-b2cbdc6b0293" xlink:to="loc_eose_AmortizationOfDebtIssuanceCostsAndDiscountsRelatedParty_9008a87d-fe2a-45a6-a152-fc16ccf4f211" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_CommitmentFeesStandbyEquityPurchaseAgreement_948032f0-18d0-4377-bcf0-891f220388fb" xlink:href="eose-20220930.xsd#eose_CommitmentFeesStandbyEquityPurchaseAgreement"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_376a57b8-7202-4949-8103-b2cbdc6b0293" xlink:to="loc_eose_CommitmentFeesStandbyEquityPurchaseAgreement_948032f0-18d0-4377-bcf0-891f220388fb" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_EmbeddedDerivativeGainLossOnEmbeddedDerivativeNetRelatedParty_5fb3b84f-7a93-4656-b2c2-79b6cbc752a3" xlink:href="eose-20220930.xsd#eose_EmbeddedDerivativeGainLossOnEmbeddedDerivativeNetRelatedParty"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_376a57b8-7202-4949-8103-b2cbdc6b0293" xlink:to="loc_eose_EmbeddedDerivativeGainLossOnEmbeddedDerivativeNetRelatedParty_5fb3b84f-7a93-4656-b2c2-79b6cbc752a3" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_0f01e754-0fb9-4353-855d-13d504a92723" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncreaseDecreaseInOperatingCapitalAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_376a57b8-7202-4949-8103-b2cbdc6b0293" xlink:to="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_0f01e754-0fb9-4353-855d-13d504a92723" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets_66ae6202-3ed6-4283-ae00-4201fe165a9b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_0f01e754-0fb9-4353-855d-13d504a92723" xlink:to="loc_us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets_66ae6202-3ed6-4283-ae00-4201fe165a9b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInInventories_337f46bf-6820-40b1-9b23-fa76d3a4a72f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncreaseDecreaseInInventories"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_0f01e754-0fb9-4353-855d-13d504a92723" xlink:to="loc_us-gaap_IncreaseDecreaseInInventories_337f46bf-6820-40b1-9b23-fa76d3a4a72f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccountsReceivable_6de6f115-7c0a-40a3-a1cd-fc204eaf6ea4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncreaseDecreaseInAccountsReceivable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_0f01e754-0fb9-4353-855d-13d504a92723" xlink:to="loc_us-gaap_IncreaseDecreaseInAccountsReceivable_6de6f115-7c0a-40a3-a1cd-fc204eaf6ea4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_IncreaseDecreaseInCurrentDepositsAssets_f71000a5-45e4-4e8a-a700-788dec632560" xlink:href="eose-20220930.xsd#eose_IncreaseDecreaseInCurrentDepositsAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_0f01e754-0fb9-4353-855d-13d504a92723" xlink:to="loc_eose_IncreaseDecreaseInCurrentDepositsAssets_f71000a5-45e4-4e8a-a700-788dec632560" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInContractWithCustomerAsset_08e67568-529b-4f2d-8449-94db7c2f6fae" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncreaseDecreaseInContractWithCustomerAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_0f01e754-0fb9-4353-855d-13d504a92723" xlink:to="loc_us-gaap_IncreaseDecreaseInContractWithCustomerAsset_08e67568-529b-4f2d-8449-94db7c2f6fae" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccountsPayable_88873808-fd6a-4db6-a431-109e0d9a94ce" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncreaseDecreaseInAccountsPayable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_0f01e754-0fb9-4353-855d-13d504a92723" xlink:to="loc_us-gaap_IncreaseDecreaseInAccountsPayable_88873808-fd6a-4db6-a431-109e0d9a94ce" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccruedLiabilities_46c93c1d-0f16-48f8-8494-ccfe9e259a2c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncreaseDecreaseInAccruedLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_0f01e754-0fb9-4353-855d-13d504a92723" xlink:to="loc_us-gaap_IncreaseDecreaseInAccruedLiabilities_46c93c1d-0f16-48f8-8494-ccfe9e259a2c" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_IncreaseDecreaseInAccountsPayableAndAccruedExpensesRelatedParty_94e72f16-c489-41ce-b6d0-db0257b5cbbd" xlink:href="eose-20220930.xsd#eose_IncreaseDecreaseInAccountsPayableAndAccruedExpensesRelatedParty"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_0f01e754-0fb9-4353-855d-13d504a92723" xlink:to="loc_eose_IncreaseDecreaseInAccountsPayableAndAccruedExpensesRelatedParty_94e72f16-c489-41ce-b6d0-db0257b5cbbd" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_IncreaseDecreaseInInterestPayableNetRelatedParty_72a46f59-d476-4553-879b-2059068977cf" xlink:href="eose-20220930.xsd#eose_IncreaseDecreaseInInterestPayableNetRelatedParty"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_0f01e754-0fb9-4353-855d-13d504a92723" xlink:to="loc_eose_IncreaseDecreaseInInterestPayableNetRelatedParty_72a46f59-d476-4553-879b-2059068977cf" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_IncreaseDecreaseInFirmPurchaseCommitments_a754ace0-bfa5-4090-9951-b53cb88ab9c0" xlink:href="eose-20220930.xsd#eose_IncreaseDecreaseInFirmPurchaseCommitments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_0f01e754-0fb9-4353-855d-13d504a92723" xlink:to="loc_eose_IncreaseDecreaseInFirmPurchaseCommitments_a754ace0-bfa5-4090-9951-b53cb88ab9c0" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOperatingLeaseLiability_96d1bfdc-f004-4022-baaf-6853b7d08a81" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncreaseDecreaseInOperatingLeaseLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_0f01e754-0fb9-4353-855d-13d504a92723" xlink:to="loc_us-gaap_IncreaseDecreaseInOperatingLeaseLiability_96d1bfdc-f004-4022-baaf-6853b7d08a81" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInContractWithCustomerLiability_643fb5ad-9922-4686-b3b9-652649ac9e16" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncreaseDecreaseInContractWithCustomerLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_0f01e754-0fb9-4353-855d-13d504a92723" xlink:to="loc_us-gaap_IncreaseDecreaseInContractWithCustomerLiability_643fb5ad-9922-4686-b3b9-652649ac9e16" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_IncreaseDecreaseInNotesPayable_b412e448-c816-49f1-9ed7-936dba8e32a6" xlink:href="eose-20220930.xsd#eose_IncreaseDecreaseInNotesPayable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_0f01e754-0fb9-4353-855d-13d504a92723" xlink:to="loc_eose_IncreaseDecreaseInNotesPayable_b412e448-c816-49f1-9ed7-936dba8e32a6" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOtherOperatingAssets_e50a8d55-bb36-480c-800e-f3df048d0d95" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncreaseDecreaseInOtherOperatingAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_0f01e754-0fb9-4353-855d-13d504a92723" xlink:to="loc_us-gaap_IncreaseDecreaseInOtherOperatingAssets_e50a8d55-bb36-480c-800e-f3df048d0d95" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_9d070d86-fe00-4080-b9b1-8821cb8f3c73" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_0cc58653-3a02-4c14-a20b-e27f9eb258bd" xlink:to="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_9d070d86-fe00-4080-b9b1-8821cb8f3c73" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_202d92fb-f4a4-4e8e-b31a-d7c7dfe99661" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_54f50675-a302-46d7-8069-b2d6b3dcb179" xlink:to="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_202d92fb-f4a4-4e8e-b31a-d7c7dfe99661" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireNotesReceivable_90409569-8624-4527-9a30-bb9907abd0e3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PaymentsToAcquireNotesReceivable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_202d92fb-f4a4-4e8e-b31a-d7c7dfe99661" xlink:to="loc_us-gaap_PaymentsToAcquireNotesReceivable_90409569-8624-4527-9a30-bb9907abd0e3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_bbf32969-8e26-42cd-988c-155e90a1ff73" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_202d92fb-f4a4-4e8e-b31a-d7c7dfe99661" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_bbf32969-8e26-42cd-988c-155e90a1ff73" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireEquityMethodInvestments_ec43e1d7-1283-4afa-88cd-5854d48c88cd" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PaymentsToAcquireEquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_202d92fb-f4a4-4e8e-b31a-d7c7dfe99661" xlink:to="loc_us-gaap_PaymentsToAcquireEquityMethodInvestments_ec43e1d7-1283-4afa-88cd-5854d48c88cd" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_288a588e-5c04-470c-9a56-074b71e08656" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PaymentsToAcquirePropertyPlantAndEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_202d92fb-f4a4-4e8e-b31a-d7c7dfe99661" xlink:to="loc_us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_288a588e-5c04-470c-9a56-074b71e08656" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_ed806905-74a8-46be-a366-b70066f046e0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_202d92fb-f4a4-4e8e-b31a-d7c7dfe99661" xlink:to="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_ed806905-74a8-46be-a366-b70066f046e0" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_981c79e9-c6e0-4627-9f03-816cb22bbfc5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_54f50675-a302-46d7-8069-b2d6b3dcb179" xlink:to="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_981c79e9-c6e0-4627-9f03-816cb22bbfc5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeasePrincipalPayments_d4d36eb0-d84e-45a9-9c46-8dde37a4cc3c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinanceLeasePrincipalPayments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_981c79e9-c6e0-4627-9f03-816cb22bbfc5" xlink:to="loc_us-gaap_FinanceLeasePrincipalPayments_d4d36eb0-d84e-45a9-9c46-8dde37a4cc3c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromStockOptionsExercised_46dc6a93-c93b-4413-b4ef-39119ca11c10" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ProceedsFromStockOptionsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_981c79e9-c6e0-4627-9f03-816cb22bbfc5" xlink:to="loc_us-gaap_ProceedsFromStockOptionsExercised_46dc6a93-c93b-4413-b4ef-39119ca11c10" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromWarrantExercises_c89c040f-2f21-4c87-a84f-fe9a80b7d32d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ProceedsFromWarrantExercises"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_981c79e9-c6e0-4627-9f03-816cb22bbfc5" xlink:to="loc_us-gaap_ProceedsFromWarrantExercises_c89c040f-2f21-4c87-a84f-fe9a80b7d32d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromRelatedPartyDebt_44da1645-24e4-487e-aeb4-34a08f323d5b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ProceedsFromRelatedPartyDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_981c79e9-c6e0-4627-9f03-816cb22bbfc5" xlink:to="loc_us-gaap_ProceedsFromRelatedPartyDebt_44da1645-24e4-487e-aeb4-34a08f323d5b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromIssuanceOfSecuredDebt_56429414-c61e-49f1-b5d2-c2a6a0ef445c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ProceedsFromIssuanceOfSecuredDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_981c79e9-c6e0-4627-9f03-816cb22bbfc5" xlink:to="loc_us-gaap_ProceedsFromIssuanceOfSecuredDebt_56429414-c61e-49f1-b5d2-c2a6a0ef445c" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsOfDebtIssuanceCosts_916cb152-ebb6-4b8b-accb-75bb8b2a1440" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PaymentsOfDebtIssuanceCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_981c79e9-c6e0-4627-9f03-816cb22bbfc5" xlink:to="loc_us-gaap_PaymentsOfDebtIssuanceCosts_916cb152-ebb6-4b8b-accb-75bb8b2a1440" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromLongTermLinesOfCredit_0da632b0-c1ce-48c7-830f-f096c2c05e21" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ProceedsFromLongTermLinesOfCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_981c79e9-c6e0-4627-9f03-816cb22bbfc5" xlink:to="loc_us-gaap_ProceedsFromLongTermLinesOfCredit_0da632b0-c1ce-48c7-830f-f096c2c05e21" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RepaymentsOfLongTermLinesOfCredit_187c17ab-6527-4cdb-ac2b-320f813f2c03" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RepaymentsOfLongTermLinesOfCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_981c79e9-c6e0-4627-9f03-816cb22bbfc5" xlink:to="loc_us-gaap_RepaymentsOfLongTermLinesOfCredit_187c17ab-6527-4cdb-ac2b-320f813f2c03" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromIssuanceOfCommonStock_0a2d7ff7-82d7-44fc-a7a0-f188062b5bbf" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ProceedsFromIssuanceOfCommonStock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_981c79e9-c6e0-4627-9f03-816cb22bbfc5" xlink:to="loc_us-gaap_ProceedsFromIssuanceOfCommonStock_0a2d7ff7-82d7-44fc-a7a0-f188062b5bbf" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation_9d14e997-ec53-4d75-b3ec-ae9243fad7c6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_981c79e9-c6e0-4627-9f03-816cb22bbfc5" xlink:to="loc_us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation_9d14e997-ec53-4d75-b3ec-ae9243fad7c6" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RepaymentsOfOtherDebt_4df4c2c6-673c-47ad-bdc9-22dbb7f23ca8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RepaymentsOfOtherDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_981c79e9-c6e0-4627-9f03-816cb22bbfc5" xlink:to="loc_us-gaap_RepaymentsOfOtherDebt_4df4c2c6-673c-47ad-bdc9-22dbb7f23ca8" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_c94b610b-1d81-40db-823c-6ffc95fcc2e1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_981c79e9-c6e0-4627-9f03-816cb22bbfc5" xlink:to="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_c94b610b-1d81-40db-823c-6ffc95fcc2e1" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_76e5f20d-42ab-4ac1-a626-6632fa257220" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_54f50675-a302-46d7-8069-b2d6b3dcb179" xlink:to="loc_us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_76e5f20d-42ab-4ac1-a626-6632fa257220" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_f58146c9-6476-4231-ab2e-5a86d12e69db" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_54f50675-a302-46d7-8069-b2d6b3dcb179" xlink:to="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_f58146c9-6476-4231-ab2e-5a86d12e69db" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_4c3d1d9c-7c61-4e4c-9648-dc2ab067c8f3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_54f50675-a302-46d7-8069-b2d6b3dcb179" xlink:to="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_4c3d1d9c-7c61-4e4c-9648-dc2ab067c8f3" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_37ede623-2f79-40e6-9b40-e6b3ac2c27ac" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_acbb0156-6e0f-4307-95f8-7e949773990b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_54f50675-a302-46d7-8069-b2d6b3dcb179" xlink:to="loc_us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_acbb0156-6e0f-4307-95f8-7e949773990b" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalExpendituresIncurredButNotYetPaid_f8b1e228-05a2-4848-91fa-c3ecddbb2a39" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CapitalExpendituresIncurredButNotYetPaid"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_acbb0156-6e0f-4307-95f8-7e949773990b" xlink:to="loc_us-gaap_CapitalExpendituresIncurredButNotYetPaid_f8b1e228-05a2-4848-91fa-c3ecddbb2a39" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssued1_720bd82c-6d06-4835-b87b-2dd995c89bfb" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockIssued1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_acbb0156-6e0f-4307-95f8-7e949773990b" xlink:to="loc_us-gaap_StockIssued1_720bd82c-6d06-4835-b87b-2dd995c89bfb" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_IssuanceOfConvertibleNotesForInterestPaidInKind_a08f3542-1f5a-4225-b4f7-9a72597697da" xlink:href="eose-20220930.xsd#eose_IssuanceOfConvertibleNotesForInterestPaidInKind"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_acbb0156-6e0f-4307-95f8-7e949773990b" xlink:to="loc_eose_IssuanceOfConvertibleNotesForInterestPaidInKind_a08f3542-1f5a-4225-b4f7-9a72597697da" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability_d7bf9b5a-12f0-4ea9-a3bc-2243fb3fe5ed" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_acbb0156-6e0f-4307-95f8-7e949773990b" xlink:to="loc_us-gaap_RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability_d7bf9b5a-12f0-4ea9-a3bc-2243fb3fe5ed" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_DebtIssuanceCostsIncurredButNotYetPaid_d7b6ad86-723c-4e1c-9c58-fe901aa5adb4" xlink:href="eose-20220930.xsd#eose_DebtIssuanceCostsIncurredButNotYetPaid"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_acbb0156-6e0f-4307-95f8-7e949773990b" xlink:to="loc_eose_DebtIssuanceCostsIncurredButNotYetPaid_d7b6ad86-723c-4e1c-9c58-fe901aa5adb4" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SupplementalCashFlowElementsAbstract_d4c6b3e1-5633-4336-8e4a-a321d78e3af1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SupplementalCashFlowElementsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_54f50675-a302-46d7-8069-b2d6b3dcb179" xlink:to="loc_us-gaap_SupplementalCashFlowElementsAbstract_d4c6b3e1-5633-4336-8e4a-a321d78e3af1" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestPaidNet_4b2a6bd0-23c1-43d6-b68a-24793d7887cf" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InterestPaidNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SupplementalCashFlowElementsAbstract_d4c6b3e1-5633-4336-8e4a-a321d78e3af1" xlink:to="loc_us-gaap_InterestPaidNet_4b2a6bd0-23c1-43d6-b68a-24793d7887cf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_c75d83c2-f272-4db8-acfb-11e9ecae53f1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_54f50675-a302-46d7-8069-b2d6b3dcb179" xlink:to="loc_us-gaap_StatementTable_c75d83c2-f272-4db8-acfb-11e9ecae53f1" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsidiarySaleOfStockAxis_d4d731f7-ca2e-4f3f-8cf2-640e51c9b0ed" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SubsidiarySaleOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_c75d83c2-f272-4db8-acfb-11e9ecae53f1" xlink:to="loc_us-gaap_SubsidiarySaleOfStockAxis_d4d731f7-ca2e-4f3f-8cf2-640e51c9b0ed" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_d4d731f7-ca2e-4f3f-8cf2-640e51c9b0ed_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SaleOfStockNameOfTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_d4d731f7-ca2e-4f3f-8cf2-640e51c9b0ed" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_d4d731f7-ca2e-4f3f-8cf2-640e51c9b0ed_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_44be24c9-3892-4722-8135-e094d596fa18" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SaleOfStockNameOfTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_d4d731f7-ca2e-4f3f-8cf2-640e51c9b0ed" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_44be24c9-3892-4722-8135-e094d596fa18" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_AtTheMarketProgramMember_97b74b03-e987-4453-a63e-e0122a183410" xlink:href="eose-20220930.xsd#eose_AtTheMarketProgramMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SaleOfStockNameOfTransactionDomain_44be24c9-3892-4722-8135-e094d596fa18" xlink:to="loc_eose_AtTheMarketProgramMember_97b74b03-e987-4453-a63e-e0122a183410" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrivatePlacementMember_9ce580c3-bfcd-48d9-a11c-d9e953d7cd78" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PrivatePlacementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SaleOfStockNameOfTransactionDomain_44be24c9-3892-4722-8135-e094d596fa18" xlink:to="loc_us-gaap_PrivatePlacementMember_9ce580c3-bfcd-48d9-a11c-d9e953d7cd78" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://eosenergystorage.com/role/NatureofOperationsandSummaryofSignificantAccountingPoliciesDetails" xlink:type="simple" xlink:href="eose-20220930.xsd#NatureofOperationsandSummaryofSignificantAccountingPoliciesDetails"/>
  <link:definitionLink xlink:role="http://eosenergystorage.com/role/NatureofOperationsandSummaryofSignificantAccountingPoliciesDetails" xlink:type="extended" id="i8d8b505e32db4cbbb2e364c376fdbb0f_NatureofOperationsandSummaryofSignificantAccountingPoliciesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProductWarrantyLiabilityLineItems_b829fbc6-9711-4a95-b79d-520e3136f80d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ProductWarrantyLiabilityLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_a00077b8-c6a9-43da-9840-48e864b8ac9c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_Assets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ProductWarrantyLiabilityLineItems_b829fbc6-9711-4a95-b79d-520e3136f80d" xlink:to="loc_us-gaap_Assets_a00077b8-c6a9-43da-9840-48e864b8ac9c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_ea98b4bb-2df8-44ae-8626-442bcf1e6536" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ProductWarrantyLiabilityLineItems_b829fbc6-9711-4a95-b79d-520e3136f80d" xlink:to="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_ea98b4bb-2df8-44ae-8626-442bcf1e6536" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Liabilities_3217445b-04d0-43e3-80dd-38ca51861629" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_Liabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ProductWarrantyLiabilityLineItems_b829fbc6-9711-4a95-b79d-520e3136f80d" xlink:to="loc_us-gaap_Liabilities_3217445b-04d0-43e3-80dd-38ca51861629" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_ConvertibleNotesPayableRelatedParty_447939a9-0e22-4569-9be6-808588dc2016" xlink:href="eose-20220930.xsd#eose_ConvertibleNotesPayableRelatedParty"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ProductWarrantyLiabilityLineItems_b829fbc6-9711-4a95-b79d-520e3136f80d" xlink:to="loc_eose_ConvertibleNotesPayableRelatedParty_447939a9-0e22-4569-9be6-808588dc2016" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLongTermDebt_3851f0cb-3228-4ff6-ab1d-fc8b45d10f81" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherLongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ProductWarrantyLiabilityLineItems_b829fbc6-9711-4a95-b79d-520e3136f80d" xlink:to="loc_us-gaap_OtherLongTermDebt_3851f0cb-3228-4ff6-ab1d-fc8b45d10f81" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsAccumulatedDeficit_c2860c77-50b1-4df5-a634-281bc5406fd5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RetainedEarningsAccumulatedDeficit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ProductWarrantyLiabilityLineItems_b829fbc6-9711-4a95-b79d-520e3136f80d" xlink:to="loc_us-gaap_RetainedEarningsAccumulatedDeficit_c2860c77-50b1-4df5-a634-281bc5406fd5" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_de88d4b7-8307-48b5-bf88-2e2ad873d0c8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ProductWarrantyLiabilityLineItems_b829fbc6-9711-4a95-b79d-520e3136f80d" xlink:to="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_de88d4b7-8307-48b5-bf88-2e2ad873d0c8" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromIssuanceOfSecuredDebt_49a7a814-5d4d-4005-a655-de5790aa8b5d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ProceedsFromIssuanceOfSecuredDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ProductWarrantyLiabilityLineItems_b829fbc6-9711-4a95-b79d-520e3136f80d" xlink:to="loc_us-gaap_ProceedsFromIssuanceOfSecuredDebt_49a7a814-5d4d-4005-a655-de5790aa8b5d" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromLongTermLinesOfCredit_a0830123-6f90-4765-8309-f4c3d0f1d64f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ProceedsFromLongTermLinesOfCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ProductWarrantyLiabilityLineItems_b829fbc6-9711-4a95-b79d-520e3136f80d" xlink:to="loc_us-gaap_ProceedsFromLongTermLinesOfCredit_a0830123-6f90-4765-8309-f4c3d0f1d64f" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_SaleOfStockAuthorizedAmountValue_afcdd78b-a1f8-4080-bcf7-7ed516749729" xlink:href="eose-20220930.xsd#eose_SaleOfStockAuthorizedAmountValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ProductWarrantyLiabilityLineItems_b829fbc6-9711-4a95-b79d-520e3136f80d" xlink:to="loc_eose_SaleOfStockAuthorizedAmountValue_afcdd78b-a1f8-4080-bcf7-7ed516749729" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_SaleOfStockPercentageOfCommissionOnGrossProceeds_7f75490e-2339-4127-af3a-1246652f3670" xlink:href="eose-20220930.xsd#eose_SaleOfStockPercentageOfCommissionOnGrossProceeds"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ProductWarrantyLiabilityLineItems_b829fbc6-9711-4a95-b79d-520e3136f80d" xlink:to="loc_eose_SaleOfStockPercentageOfCommissionOnGrossProceeds_7f75490e-2339-4127-af3a-1246652f3670" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction_f30e45d0-feca-4741-946f-308fe2fdbc8e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ProductWarrantyLiabilityLineItems_b829fbc6-9711-4a95-b79d-520e3136f80d" xlink:to="loc_us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction_f30e45d0-feca-4741-946f-308fe2fdbc8e" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromIssuanceOfCommonStock_0bf699d5-4b14-443a-b35d-11f15ba7b521" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ProceedsFromIssuanceOfCommonStock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ProductWarrantyLiabilityLineItems_b829fbc6-9711-4a95-b79d-520e3136f80d" xlink:to="loc_us-gaap_ProceedsFromIssuanceOfCommonStock_0bf699d5-4b14-443a-b35d-11f15ba7b521" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockConsiderationReceivedOnTransaction_c5474067-9227-46c9-a084-1299122f37bd" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SaleOfStockConsiderationReceivedOnTransaction"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ProductWarrantyLiabilityLineItems_b829fbc6-9711-4a95-b79d-520e3136f80d" xlink:to="loc_us-gaap_SaleOfStockConsiderationReceivedOnTransaction_c5474067-9227-46c9-a084-1299122f37bd" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockPricePerShare_5d601b4b-3b84-4bea-b0aa-2483ede54001" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SaleOfStockPricePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ProductWarrantyLiabilityLineItems_b829fbc6-9711-4a95-b79d-520e3136f80d" xlink:to="loc_us-gaap_SaleOfStockPricePerShare_5d601b4b-3b84-4bea-b0aa-2483ede54001" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_SaleOfStockAgreementTerm_93b34cd5-9df6-4493-9526-e6340e5ed093" xlink:href="eose-20220930.xsd#eose_SaleOfStockAgreementTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ProductWarrantyLiabilityLineItems_b829fbc6-9711-4a95-b79d-520e3136f80d" xlink:to="loc_eose_SaleOfStockAgreementTerm_93b34cd5-9df6-4493-9526-e6340e5ed093" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_SharePriceAsPercentageOfMarketPrice_7b1e34bc-cf92-4900-a525-655cd81556ff" xlink:href="eose-20220930.xsd#eose_SharePriceAsPercentageOfMarketPrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ProductWarrantyLiabilityLineItems_b829fbc6-9711-4a95-b79d-520e3136f80d" xlink:to="loc_eose_SharePriceAsPercentageOfMarketPrice_7b1e34bc-cf92-4900-a525-655cd81556ff" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromSaleOfTreasuryStock_32edda6d-422b-4e94-aa7c-1d1e76f8e708" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ProceedsFromSaleOfTreasuryStock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ProductWarrantyLiabilityLineItems_b829fbc6-9711-4a95-b79d-520e3136f80d" xlink:to="loc_us-gaap_ProceedsFromSaleOfTreasuryStock_32edda6d-422b-4e94-aa7c-1d1e76f8e708" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseRightOfUseAsset_bee8075b-c279-45fb-b259-bc9947c5d32f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OperatingLeaseRightOfUseAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ProductWarrantyLiabilityLineItems_b829fbc6-9711-4a95-b79d-520e3136f80d" xlink:to="loc_us-gaap_OperatingLeaseRightOfUseAsset_bee8075b-c279-45fb-b259-bc9947c5d32f" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiability_3cea50cf-b6f3-4fcb-9850-50e61c9406c2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OperatingLeaseLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ProductWarrantyLiabilityLineItems_b829fbc6-9711-4a95-b79d-520e3136f80d" xlink:to="loc_us-gaap_OperatingLeaseLiability_3cea50cf-b6f3-4fcb-9850-50e61c9406c2" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsidiaryOrEquityMethodInvesteeSaleOfStockBySubsidiaryOrEquityInvesteeTable_e3133b21-2cd2-4b15-88b6-9d736a296530" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SubsidiaryOrEquityMethodInvesteeSaleOfStockBySubsidiaryOrEquityInvesteeTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ProductWarrantyLiabilityLineItems_b829fbc6-9711-4a95-b79d-520e3136f80d" xlink:to="loc_us-gaap_SubsidiaryOrEquityMethodInvesteeSaleOfStockBySubsidiaryOrEquityInvesteeTable_e3133b21-2cd2-4b15-88b6-9d736a296530" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_47b4a3da-4f90-4e0a-b893-51fad74cd17a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsidiaryOrEquityMethodInvesteeSaleOfStockBySubsidiaryOrEquityInvesteeTable_e3133b21-2cd2-4b15-88b6-9d736a296530" xlink:to="loc_us-gaap_DebtInstrumentAxis_47b4a3da-4f90-4e0a-b893-51fad74cd17a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_47b4a3da-4f90-4e0a-b893-51fad74cd17a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_47b4a3da-4f90-4e0a-b893-51fad74cd17a" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_47b4a3da-4f90-4e0a-b893-51fad74cd17a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_8130aa30-5889-43c8-ad12-2d04a3649839" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_47b4a3da-4f90-4e0a-b893-51fad74cd17a" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_8130aa30-5889-43c8-ad12-2d04a3649839" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_SeniorSecuredTermLoanAgreementMember_71accdde-2d9a-4619-b256-eab7fee7eb45" xlink:href="eose-20220930.xsd#eose_SeniorSecuredTermLoanAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_8130aa30-5889-43c8-ad12-2d04a3649839" xlink:to="loc_eose_SeniorSecuredTermLoanAgreementMember_71accdde-2d9a-4619-b256-eab7fee7eb45" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_EquipmentFinancingFacilityMember_32345ec6-599b-46f1-969e-861ad3f0b82a" xlink:href="eose-20220930.xsd#eose_EquipmentFinancingFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_8130aa30-5889-43c8-ad12-2d04a3649839" xlink:to="loc_eose_EquipmentFinancingFacilityMember_32345ec6-599b-46f1-969e-861ad3f0b82a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsidiarySaleOfStockAxis_dda8a2e1-4c52-494b-9f45-932b84560404" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SubsidiarySaleOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsidiaryOrEquityMethodInvesteeSaleOfStockBySubsidiaryOrEquityInvesteeTable_e3133b21-2cd2-4b15-88b6-9d736a296530" xlink:to="loc_us-gaap_SubsidiarySaleOfStockAxis_dda8a2e1-4c52-494b-9f45-932b84560404" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_dda8a2e1-4c52-494b-9f45-932b84560404_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SaleOfStockNameOfTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_dda8a2e1-4c52-494b-9f45-932b84560404" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_dda8a2e1-4c52-494b-9f45-932b84560404_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_647af54e-6da5-4f5d-84dc-7b724b433b52" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SaleOfStockNameOfTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_dda8a2e1-4c52-494b-9f45-932b84560404" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_647af54e-6da5-4f5d-84dc-7b724b433b52" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_AtTheMarketProgramMember_9fa4994c-24b9-4112-8d9e-35430dc7da98" xlink:href="eose-20220930.xsd#eose_AtTheMarketProgramMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SaleOfStockNameOfTransactionDomain_647af54e-6da5-4f5d-84dc-7b724b433b52" xlink:to="loc_eose_AtTheMarketProgramMember_9fa4994c-24b9-4112-8d9e-35430dc7da98" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrivatePlacementMember_18cedc19-967d-4f94-bd2d-64cac9424992" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PrivatePlacementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SaleOfStockNameOfTransactionDomain_647af54e-6da5-4f5d-84dc-7b724b433b52" xlink:to="loc_us-gaap_PrivatePlacementMember_18cedc19-967d-4f94-bd2d-64cac9424992" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_4b2e84be-6560-4db1-b459-20b2cb28c4be" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsidiaryOrEquityMethodInvesteeSaleOfStockBySubsidiaryOrEquityInvesteeTable_e3133b21-2cd2-4b15-88b6-9d736a296530" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_4b2e84be-6560-4db1-b459-20b2cb28c4be" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_4b2e84be-6560-4db1-b459-20b2cb28c4be_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_4b2e84be-6560-4db1-b459-20b2cb28c4be" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_4b2e84be-6560-4db1-b459-20b2cb28c4be_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_0f3eb124-a3de-453e-b783-306dbba56a01" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_4b2e84be-6560-4db1-b459-20b2cb28c4be" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_0f3eb124-a3de-453e-b783-306dbba56a01" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebtMember_49a0fe3f-33a8-4c74-9f41-17aeb7ad983f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_0f3eb124-a3de-453e-b783-306dbba56a01" xlink:to="loc_us-gaap_SecuredDebtMember_49a0fe3f-33a8-4c74-9f41-17aeb7ad983f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_9280c1b8-2e06-4517-be39-5050aed7e08d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_0f3eb124-a3de-453e-b783-306dbba56a01" xlink:to="loc_us-gaap_LineOfCreditMember_9280c1b8-2e06-4517-be39-5050aed7e08d" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://eosenergystorage.com/role/AcquisitionNarrativeDetails" xlink:type="simple" xlink:href="eose-20220930.xsd#AcquisitionNarrativeDetails"/>
  <link:definitionLink xlink:role="http://eosenergystorage.com/role/AcquisitionNarrativeDetails" xlink:type="extended" id="i3402fcb656df45c6858b3f845b0d1648_AcquisitionNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_03dcf7e4-dd0f-4116-9180-223ff9ad6808" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessAcquisitionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired_d4fac24c-d39b-4530-b7e3-4a400b33b124" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_03dcf7e4-dd0f-4116-9180-223ff9ad6808" xlink:to="loc_us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired_d4fac24c-d39b-4530-b7e3-4a400b33b124" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_4f0b4993-7029-4ad0-bcc3-5f0b28cc63e3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityMethodInvestmentOwnershipPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_03dcf7e4-dd0f-4116-9180-223ff9ad6808" xlink:to="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_4f0b4993-7029-4ad0-bcc3-5f0b28cc63e3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferred1_8a7fce97-6571-4323-8072-480caa6f0492" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessCombinationConsiderationTransferred1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_03dcf7e4-dd0f-4116-9180-223ff9ad6808" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferred1_8a7fce97-6571-4323-8072-480caa6f0492" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_BusinessCombinationConsiderationTransferredRemainderOfFiscalYear_ba7f9f50-f9e2-408a-b3ba-d169e9d4074d" xlink:href="eose-20220930.xsd#eose_BusinessCombinationConsiderationTransferredRemainderOfFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_03dcf7e4-dd0f-4116-9180-223ff9ad6808" xlink:to="loc_eose_BusinessCombinationConsiderationTransferredRemainderOfFiscalYear_ba7f9f50-f9e2-408a-b3ba-d169e9d4074d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_BusinessCombinationConsiderationTransferredYearOne_f946efef-2aae-4d4e-a7e4-f60411e62850" xlink:href="eose-20220930.xsd#eose_BusinessCombinationConsiderationTransferredYearOne"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_03dcf7e4-dd0f-4116-9180-223ff9ad6808" xlink:to="loc_eose_BusinessCombinationConsiderationTransferredYearOne_f946efef-2aae-4d4e-a7e4-f60411e62850" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_BusinessCombinationConsiderationTransferredYearTwo_69e5fe6c-c379-495c-b54b-c274080cd855" xlink:href="eose-20220930.xsd#eose_BusinessCombinationConsiderationTransferredYearTwo"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_03dcf7e4-dd0f-4116-9180-223ff9ad6808" xlink:to="loc_eose_BusinessCombinationConsiderationTransferredYearTwo_69e5fe6c-c379-495c-b54b-c274080cd855" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_BusinessCombinationConsiderationTransferredYearThree_8db1c1cd-593a-4c01-9c6b-30f47ba60cfe" xlink:href="eose-20220930.xsd#eose_BusinessCombinationConsiderationTransferredYearThree"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_03dcf7e4-dd0f-4116-9180-223ff9ad6808" xlink:to="loc_eose_BusinessCombinationConsiderationTransferredYearThree_8db1c1cd-593a-4c01-9c6b-30f47ba60cfe" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_BusinessCombinationConsiderationTransferredYearFour_75627dd6-2fad-4220-aecf-7539d1446936" xlink:href="eose-20220930.xsd#eose_BusinessCombinationConsiderationTransferredYearFour"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_03dcf7e4-dd0f-4116-9180-223ff9ad6808" xlink:to="loc_eose_BusinessCombinationConsiderationTransferredYearFour_75627dd6-2fad-4220-aecf-7539d1446936" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_2a75f3f5-7531-4ed0-8af9-cd22b202e7d1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_03dcf7e4-dd0f-4116-9180-223ff9ad6808" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_2a75f3f5-7531-4ed0-8af9-cd22b202e7d1" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainsLossesOnExtinguishmentOfDebt_d1db380b-bf9d-46db-bc31-69c3d28fd5e0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_GainsLossesOnExtinguishmentOfDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_03dcf7e4-dd0f-4116-9180-223ff9ad6808" xlink:to="loc_us-gaap_GainsLossesOnExtinguishmentOfDebt_d1db380b-bf9d-46db-bc31-69c3d28fd5e0" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_ConsiderationTransferredFairValue_4ef0c07b-f9fe-4eb3-9af2-016dcef29b67" xlink:href="eose-20220930.xsd#eose_ConsiderationTransferredFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_03dcf7e4-dd0f-4116-9180-223ff9ad6808" xlink:to="loc_eose_ConsiderationTransferredFairValue_4ef0c07b-f9fe-4eb3-9af2-016dcef29b67" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_PaymentToTerminateAgreement_39cbf117-c4f5-463c-9a3f-63302aca11da" xlink:href="eose-20220930.xsd#eose_PaymentToTerminateAgreement"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_03dcf7e4-dd0f-4116-9180-223ff9ad6808" xlink:to="loc_eose_PaymentToTerminateAgreement_39cbf117-c4f5-463c-9a3f-63302aca11da" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnContractTermination_19647dd4-d416-499d-ad67-af0ed8bbba9e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_GainLossOnContractTermination"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_03dcf7e4-dd0f-4116-9180-223ff9ad6808" xlink:to="loc_us-gaap_GainLossOnContractTermination_19647dd4-d416-499d-ad67-af0ed8bbba9e" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferredIncludingEquityInterestInAcquireeHeldPriorToCombination1_1d51f47f-331a-4436-abbc-4f6ab73a7512" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessCombinationConsiderationTransferredIncludingEquityInterestInAcquireeHeldPriorToCombination1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_03dcf7e4-dd0f-4116-9180-223ff9ad6808" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferredIncludingEquityInterestInAcquireeHeldPriorToCombination1_1d51f47f-331a-4436-abbc-4f6ab73a7512" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationStepAcquisitionEquityInterestInAcquireeFairValue1_b6bca9d6-c884-404c-8e19-fdb84a26f4e4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessCombinationStepAcquisitionEquityInterestInAcquireeFairValue1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_03dcf7e4-dd0f-4116-9180-223ff9ad6808" xlink:to="loc_us-gaap_BusinessCombinationStepAcquisitionEquityInterestInAcquireeFairValue1_b6bca9d6-c884-404c-8e19-fdb84a26f4e4" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationStepAcquisitionEquityInterestInAcquireeRemeasurementLoss_76b1c212-1f8c-4697-8d60-88544d635bd3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessCombinationStepAcquisitionEquityInterestInAcquireeRemeasurementLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_03dcf7e4-dd0f-4116-9180-223ff9ad6808" xlink:to="loc_us-gaap_BusinessCombinationStepAcquisitionEquityInterestInAcquireeRemeasurementLoss_76b1c212-1f8c-4697-8d60-88544d635bd3" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_0314bb0c-c352-4316-aa3b-5e8f726b972c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_03dcf7e4-dd0f-4116-9180-223ff9ad6808" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_0314bb0c-c352-4316-aa3b-5e8f726b972c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_fe646733-5bf7-459a-b9e0-2aba2e1adb34" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_0314bb0c-c352-4316-aa3b-5e8f726b972c" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_fe646733-5bf7-459a-b9e0-2aba2e1adb34" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_fe646733-5bf7-459a-b9e0-2aba2e1adb34_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_fe646733-5bf7-459a-b9e0-2aba2e1adb34" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_fe646733-5bf7-459a-b9e0-2aba2e1adb34_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_7856b8ae-595d-449a-afc0-a3c8b255629e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_fe646733-5bf7-459a-b9e0-2aba2e1adb34" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_7856b8ae-595d-449a-afc0-a3c8b255629e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_HIPOWERLLCMember_aadebefa-094e-450b-92cc-103952bb34ae" xlink:href="eose-20220930.xsd#eose_HIPOWERLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_7856b8ae-595d-449a-afc0-a3c8b255629e" xlink:to="loc_eose_HIPOWERLLCMember_aadebefa-094e-450b-92cc-103952bb34ae" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_0049b650-69ab-4357-8045-2bf63fc18ab6" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_0314bb0c-c352-4316-aa3b-5e8f726b972c" xlink:to="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_0049b650-69ab-4357-8045-2bf63fc18ab6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_0049b650-69ab-4357-8045-2bf63fc18ab6_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_0049b650-69ab-4357-8045-2bf63fc18ab6" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_0049b650-69ab-4357-8045-2bf63fc18ab6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_a84faf8d-65e1-441e-8584-af3a17b9e8da" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_0049b650-69ab-4357-8045-2bf63fc18ab6" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_a84faf8d-65e1-441e-8584-af3a17b9e8da" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_HIPOWERLLCMember_f24e637d-5111-41a6-9795-b05121465369" xlink:href="eose-20220930.xsd#eose_HIPOWERLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_a84faf8d-65e1-441e-8584-af3a17b9e8da" xlink:to="loc_eose_HIPOWERLLCMember_f24e637d-5111-41a6-9795-b05121465369" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CounterpartyNameAxis_9e8ecf3e-3ae2-4048-b670-8d97e164ae76" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_CounterpartyNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_0314bb0c-c352-4316-aa3b-5e8f726b972c" xlink:to="loc_srt_CounterpartyNameAxis_9e8ecf3e-3ae2-4048-b670-8d97e164ae76" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_9e8ecf3e-3ae2-4048-b670-8d97e164ae76_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_9e8ecf3e-3ae2-4048-b670-8d97e164ae76" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_9e8ecf3e-3ae2-4048-b670-8d97e164ae76_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_ed1e98ce-2726-4460-ae63-6c02ae653c63" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_9e8ecf3e-3ae2-4048-b670-8d97e164ae76" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_ed1e98ce-2726-4460-ae63-6c02ae653c63" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_HoltecPowerIncMember_629ca437-4fb3-4655-96f5-1ad7014597ef" xlink:href="eose-20220930.xsd#eose_HoltecPowerIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_ed1e98ce-2726-4460-ae63-6c02ae653c63" xlink:to="loc_eose_HoltecPowerIncMember_629ca437-4fb3-4655-96f5-1ad7014597ef" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://eosenergystorage.com/role/AcquisitionRelatedFairValuesDetails" xlink:type="simple" xlink:href="eose-20220930.xsd#AcquisitionRelatedFairValuesDetails"/>
  <link:definitionLink xlink:role="http://eosenergystorage.com/role/AcquisitionRelatedFairValuesDetails" xlink:type="extended" id="ic1dbcaf820424325ba97128773e4079a_AcquisitionRelatedFairValuesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_039487f5-1662-4c76-a6f2-cfd1930051c3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessAcquisitionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedInventory_6adffb3a-fc6f-403e-b55b-f390d8bdbb42" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedInventory"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_039487f5-1662-4c76-a6f2-cfd1930051c3" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedInventory_6adffb3a-fc6f-403e-b55b-f390d8bdbb42" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsOther_1167b43f-1993-47dd-9c7f-aac392332c44" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsOther"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_039487f5-1662-4c76-a6f2-cfd1930051c3" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsOther_1167b43f-1993-47dd-9c7f-aac392332c44" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment_4b34cf30-c3f3-40aa-ad4a-11b28945c045" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_039487f5-1662-4c76-a6f2-cfd1930051c3" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment_4b34cf30-c3f3-40aa-ad4a-11b28945c045" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_a107e812-5440-4dc6-9f3e-1b1a4647d6ff" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_039487f5-1662-4c76-a6f2-cfd1930051c3" xlink:to="loc_us-gaap_Goodwill_a107e812-5440-4dc6-9f3e-1b1a4647d6ff" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesAccountsPayable_4843adde-720a-4f23-9a51-a43c95724650" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesAccountsPayable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_039487f5-1662-4c76-a6f2-cfd1930051c3" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesAccountsPayable_4843adde-720a-4f23-9a51-a43c95724650" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesOther_f07c0205-532a-4ba8-b319-fadeb32103cc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesOther"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_039487f5-1662-4c76-a6f2-cfd1930051c3" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesOther_f07c0205-532a-4ba8-b319-fadeb32103cc" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet_04f1e989-3580-40d8-8d97-c722c776b5c9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_039487f5-1662-4c76-a6f2-cfd1930051c3" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet_04f1e989-3580-40d8-8d97-c722c776b5c9" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents_aad6aa18-3ef4-434e-9a50-96142d737e0a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_039487f5-1662-4c76-a6f2-cfd1930051c3" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents_aad6aa18-3ef4-434e-9a50-96142d737e0a" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_a69ff85e-fa3f-4220-bd1e-ae03f644a3fd" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_039487f5-1662-4c76-a6f2-cfd1930051c3" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_a69ff85e-fa3f-4220-bd1e-ae03f644a3fd" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_02f1318e-0311-495e-8394-cb9d718e6911" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_a69ff85e-fa3f-4220-bd1e-ae03f644a3fd" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_02f1318e-0311-495e-8394-cb9d718e6911" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_02f1318e-0311-495e-8394-cb9d718e6911_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_02f1318e-0311-495e-8394-cb9d718e6911" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_02f1318e-0311-495e-8394-cb9d718e6911_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_34403c27-3138-4551-bbb5-59c43914e756" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_02f1318e-0311-495e-8394-cb9d718e6911" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_34403c27-3138-4551-bbb5-59c43914e756" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_HIPOWERLLCMember_a3f48ed3-a829-44de-9985-49631644fff8" xlink:href="eose-20220930.xsd#eose_HIPOWERLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_34403c27-3138-4551-bbb5-59c43914e756" xlink:to="loc_eose_HIPOWERLLCMember_a3f48ed3-a829-44de-9985-49631644fff8" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://eosenergystorage.com/role/RevenueRecognitionRevenueRecognitionTableDetails" xlink:type="simple" xlink:href="eose-20220930.xsd#RevenueRecognitionRevenueRecognitionTableDetails"/>
  <link:definitionLink xlink:role="http://eosenergystorage.com/role/RevenueRecognitionRevenueRecognitionTableDetails" xlink:type="extended" id="i477272f1bc2f4bc6ae9c03e00df125c7_RevenueRecognitionRevenueRecognitionTableDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_edaa2920-5c33-4ee0-9a44-401f6e1fe8af" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_80ae01d7-53da-4f3d-892c-163293056518" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_edaa2920-5c33-4ee0-9a44-401f6e1fe8af" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_80ae01d7-53da-4f3d-892c-163293056518" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_8715bcba-4ce6-4bdf-aa8f-d9138994241a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_edaa2920-5c33-4ee0-9a44-401f6e1fe8af" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_8715bcba-4ce6-4bdf-aa8f-d9138994241a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TimingOfTransferOfGoodOrServiceAxis_cd862a84-6a26-449a-9a82-8edf99a84af1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TimingOfTransferOfGoodOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_8715bcba-4ce6-4bdf-aa8f-d9138994241a" xlink:to="loc_us-gaap_TimingOfTransferOfGoodOrServiceAxis_cd862a84-6a26-449a-9a82-8edf99a84af1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TimingOfTransferOfGoodOrServiceDomain_cd862a84-6a26-449a-9a82-8edf99a84af1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TimingOfTransferOfGoodOrServiceDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_TimingOfTransferOfGoodOrServiceAxis_cd862a84-6a26-449a-9a82-8edf99a84af1" xlink:to="loc_us-gaap_TimingOfTransferOfGoodOrServiceDomain_cd862a84-6a26-449a-9a82-8edf99a84af1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TimingOfTransferOfGoodOrServiceDomain_96433628-91a7-4756-8f0d-5e69c9760ec0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TimingOfTransferOfGoodOrServiceDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_TimingOfTransferOfGoodOrServiceAxis_cd862a84-6a26-449a-9a82-8edf99a84af1" xlink:to="loc_us-gaap_TimingOfTransferOfGoodOrServiceDomain_96433628-91a7-4756-8f0d-5e69c9760ec0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransferredAtPointInTimeMember_3908c462-54ba-442b-9c5f-89631f7300b5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TransferredAtPointInTimeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TimingOfTransferOfGoodOrServiceDomain_96433628-91a7-4756-8f0d-5e69c9760ec0" xlink:to="loc_us-gaap_TransferredAtPointInTimeMember_3908c462-54ba-442b-9c5f-89631f7300b5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransferredOverTimeMember_4181ea22-ca45-4574-b360-e1d69e29cd56" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TransferredOverTimeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TimingOfTransferOfGoodOrServiceDomain_96433628-91a7-4756-8f0d-5e69c9760ec0" xlink:to="loc_us-gaap_TransferredOverTimeMember_4181ea22-ca45-4574-b360-e1d69e29cd56" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://eosenergystorage.com/role/RevenueRecognitionNarrativesDetails" xlink:type="simple" xlink:href="eose-20220930.xsd#RevenueRecognitionNarrativesDetails"/>
  <link:definitionLink xlink:role="http://eosenergystorage.com/role/RevenueRecognitionNarrativesDetails" xlink:type="extended" id="ia1bb549c7d1d4e2ca005d764006a1a25_RevenueRecognitionNarrativesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_dc573bae-9686-4971-a8fe-79fab3bb52f3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossOnContracts_d7e9f70a-655d-4c7b-b939-b8f4d20562dd" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LossOnContracts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_dc573bae-9686-4971-a8fe-79fab3bb52f3" xlink:to="loc_us-gaap_LossOnContracts_d7e9f70a-655d-4c7b-b939-b8f4d20562dd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskPercentage1_a7b69102-79f7-40cb-911b-bb6eb2479437" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ConcentrationRiskPercentage1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_dc573bae-9686-4971-a8fe-79fab3bb52f3" xlink:to="loc_us-gaap_ConcentrationRiskPercentage1_a7b69102-79f7-40cb-911b-bb6eb2479437" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInContractWithCustomerAsset_a49de0da-278e-49df-abc0-059a41120feb" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncreaseDecreaseInContractWithCustomerAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_dc573bae-9686-4971-a8fe-79fab3bb52f3" xlink:to="loc_us-gaap_IncreaseDecreaseInContractWithCustomerAsset_a49de0da-278e-49df-abc0-059a41120feb" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInContractWithCustomerLiability_16545688-71d8-4994-adc9-122cf9f285d6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncreaseDecreaseInContractWithCustomerLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_dc573bae-9686-4971-a8fe-79fab3bb52f3" xlink:to="loc_us-gaap_IncreaseDecreaseInContractWithCustomerLiability_16545688-71d8-4994-adc9-122cf9f285d6" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_ContractWithCustomerLiabilityIncreaseDueToAdvancePayments_8125ff96-b525-4e2f-a235-aba823b8c2c7" xlink:href="eose-20220930.xsd#eose_ContractWithCustomerLiabilityIncreaseDueToAdvancePayments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_dc573bae-9686-4971-a8fe-79fab3bb52f3" xlink:to="loc_eose_ContractWithCustomerLiabilityIncreaseDueToAdvancePayments_8125ff96-b525-4e2f-a235-aba823b8c2c7" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityRevenueRecognized_f266661c-2b3e-4619-86df-9629a030e298" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ContractWithCustomerLiabilityRevenueRecognized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_dc573bae-9686-4971-a8fe-79fab3bb52f3" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityRevenueRecognized_f266661c-2b3e-4619-86df-9629a030e298" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityCurrent_381c5887-e1a6-4d10-9c24-b5013982ef4f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ContractWithCustomerLiabilityCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_dc573bae-9686-4971-a8fe-79fab3bb52f3" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityCurrent_381c5887-e1a6-4d10-9c24-b5013982ef4f" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityNoncurrent_1abd10fd-3cf4-4bce-a23b-e45f10b410ae" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ContractWithCustomerLiabilityNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_dc573bae-9686-4971-a8fe-79fab3bb52f3" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityNoncurrent_1abd10fd-3cf4-4bce-a23b-e45f10b410ae" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalizedContractCostNetCurrent_b1ec56af-873d-479f-b38b-46d9812f6bd0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CapitalizedContractCostNetCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_dc573bae-9686-4971-a8fe-79fab3bb52f3" xlink:to="loc_us-gaap_CapitalizedContractCostNetCurrent_b1ec56af-873d-479f-b38b-46d9812f6bd0" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalizedContractCostNetNoncurrent_45486cd9-3f8a-43fa-8dd6-01ec50499903" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CapitalizedContractCostNetNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_dc573bae-9686-4971-a8fe-79fab3bb52f3" xlink:to="loc_us-gaap_CapitalizedContractCostNetNoncurrent_45486cd9-3f8a-43fa-8dd6-01ec50499903" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_d1426b10-6ec6-4446-8fb1-978ae524aed1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_dc573bae-9686-4971-a8fe-79fab3bb52f3" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_d1426b10-6ec6-4446-8fb1-978ae524aed1" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_0bcb5252-1632-4e2f-ae8e-d4282068d541" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_d1426b10-6ec6-4446-8fb1-978ae524aed1" xlink:to="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_0bcb5252-1632-4e2f-ae8e-d4282068d541" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_0bcb5252-1632-4e2f-ae8e-d4282068d541_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_0bcb5252-1632-4e2f-ae8e-d4282068d541" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_0bcb5252-1632-4e2f-ae8e-d4282068d541_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_c7cecad4-077d-478d-9e32-99886b44756d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_0bcb5252-1632-4e2f-ae8e-d4282068d541" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_c7cecad4-077d-478d-9e32-99886b44756d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SalesRevenueNetMember_8c2c5d0b-de1d-43ba-95dc-903df19e0ee3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SalesRevenueNetMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_c7cecad4-077d-478d-9e32-99886b44756d" xlink:to="loc_us-gaap_SalesRevenueNetMember_8c2c5d0b-de1d-43ba-95dc-903df19e0ee3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MajorCustomersAxis_122a07f4-97c4-4847-9cfd-f7e180b3632b" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_MajorCustomersAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_d1426b10-6ec6-4446-8fb1-978ae524aed1" xlink:to="loc_srt_MajorCustomersAxis_122a07f4-97c4-4847-9cfd-f7e180b3632b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NameOfMajorCustomerDomain_122a07f4-97c4-4847-9cfd-f7e180b3632b_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_NameOfMajorCustomerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_MajorCustomersAxis_122a07f4-97c4-4847-9cfd-f7e180b3632b" xlink:to="loc_srt_NameOfMajorCustomerDomain_122a07f4-97c4-4847-9cfd-f7e180b3632b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NameOfMajorCustomerDomain_bd2f237b-fdf0-41bb-8eee-939bce299153" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_NameOfMajorCustomerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_MajorCustomersAxis_122a07f4-97c4-4847-9cfd-f7e180b3632b" xlink:to="loc_srt_NameOfMajorCustomerDomain_bd2f237b-fdf0-41bb-8eee-939bce299153" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_Customer1Member_e5e0ee16-e288-4456-a527-ba5f99c7ca58" xlink:href="eose-20220930.xsd#eose_Customer1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_bd2f237b-fdf0-41bb-8eee-939bce299153" xlink:to="loc_eose_Customer1Member_e5e0ee16-e288-4456-a527-ba5f99c7ca58" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_Customer2Member_1328bc2a-a23b-45da-8504-c7432b2d2b43" xlink:href="eose-20220930.xsd#eose_Customer2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_bd2f237b-fdf0-41bb-8eee-939bce299153" xlink:to="loc_eose_Customer2Member_1328bc2a-a23b-45da-8504-c7432b2d2b43" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_Customer3Member_5c538eb3-5641-4cc1-8e8f-f0c8ae77dc2a" xlink:href="eose-20220930.xsd#eose_Customer3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_bd2f237b-fdf0-41bb-8eee-939bce299153" xlink:to="loc_eose_Customer3Member_5c538eb3-5641-4cc1-8e8f-f0c8ae77dc2a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByTypeAxis_0b75664c-add5-4167-ad91-3567655d4613" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ConcentrationRiskByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_d1426b10-6ec6-4446-8fb1-978ae524aed1" xlink:to="loc_us-gaap_ConcentrationRiskByTypeAxis_0b75664c-add5-4167-ad91-3567655d4613" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_0b75664c-add5-4167-ad91-3567655d4613_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_0b75664c-add5-4167-ad91-3567655d4613" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_0b75664c-add5-4167-ad91-3567655d4613_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_8daa79c6-91cc-4d3f-949f-c1a8cee5f121" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_0b75664c-add5-4167-ad91-3567655d4613" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_8daa79c6-91cc-4d3f-949f-c1a8cee5f121" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerConcentrationRiskMember_7bc2e312-ab34-4a6a-b52a-113345be4b9a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CustomerConcentrationRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_8daa79c6-91cc-4d3f-949f-c1a8cee5f121" xlink:to="loc_us-gaap_CustomerConcentrationRiskMember_7bc2e312-ab34-4a6a-b52a-113345be4b9a" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://eosenergystorage.com/role/PropertyPlantandEquipmentNetComponentsofPropertyandEquipmentDetails" xlink:type="simple" xlink:href="eose-20220930.xsd#PropertyPlantandEquipmentNetComponentsofPropertyandEquipmentDetails"/>
  <link:definitionLink xlink:role="http://eosenergystorage.com/role/PropertyPlantandEquipmentNetComponentsofPropertyandEquipmentDetails" xlink:type="extended" id="i7c15747616f048fd83fa4128c2318f65_PropertyPlantandEquipmentNetComponentsofPropertyandEquipmentDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentLineItems_4bfbd2fb-e029-4450-b7df-aa0ecf2fc4ef" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PropertyPlantAndEquipmentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetBeforeAccumulatedDepreciationAndAmortization_81e1edfd-d661-4487-9f33-462b732db671" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetBeforeAccumulatedDepreciationAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_4bfbd2fb-e029-4450-b7df-aa0ecf2fc4ef" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetBeforeAccumulatedDepreciationAndAmortization_81e1edfd-d661-4487-9f33-462b732db671" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAccumulatedDepreciationAndAmortization_af0c0e51-7c37-4e85-81f1-91fb2f1abd45" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAccumulatedDepreciationAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_4bfbd2fb-e029-4450-b7df-aa0ecf2fc4ef" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAccumulatedDepreciationAndAmortization_af0c0e51-7c37-4e85-81f1-91fb2f1abd45" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization_01434103-affa-4092-8ab4-d2837d96add7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_4bfbd2fb-e029-4450-b7df-aa0ecf2fc4ef" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization_01434103-affa-4092-8ab4-d2837d96add7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentUsefulLife_022daabf-cf03-4f65-a1ba-dcebd54ba598" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PropertyPlantAndEquipmentUsefulLife"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_4bfbd2fb-e029-4450-b7df-aa0ecf2fc4ef" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentUsefulLife_022daabf-cf03-4f65-a1ba-dcebd54ba598" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_bf1785be-dc2e-479a-b846-152c84dfb63f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_4bfbd2fb-e029-4450-b7df-aa0ecf2fc4ef" xlink:to="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_bf1785be-dc2e-479a-b846-152c84dfb63f" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_e10ed1b3-f9dd-4719-ad83-0a7ae7c2cdf9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_bf1785be-dc2e-479a-b846-152c84dfb63f" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_e10ed1b3-f9dd-4719-ad83-0a7ae7c2cdf9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_e10ed1b3-f9dd-4719-ad83-0a7ae7c2cdf9_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_e10ed1b3-f9dd-4719-ad83-0a7ae7c2cdf9" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_e10ed1b3-f9dd-4719-ad83-0a7ae7c2cdf9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_f7c0398a-c122-4307-be2d-4f91a67fa85a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_e10ed1b3-f9dd-4719-ad83-0a7ae7c2cdf9" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_f7c0398a-c122-4307-be2d-4f91a67fa85a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquipmentMember_47aab879-59b2-424c-8f17-ec1881a6e138" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquipmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_f7c0398a-c122-4307-be2d-4f91a67fa85a" xlink:to="loc_us-gaap_EquipmentMember_47aab879-59b2-424c-8f17-ec1881a6e138" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_FinanceLeaseMember_f2f54d9c-e791-4e57-9ab1-a4c633870160" xlink:href="eose-20220930.xsd#eose_FinanceLeaseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_f7c0398a-c122-4307-be2d-4f91a67fa85a" xlink:to="loc_eose_FinanceLeaseMember_f2f54d9c-e791-4e57-9ab1-a4c633870160" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FurnitureAndFixturesMember_1cff351a-0a43-45e4-8865-7e1f80c10bdd" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FurnitureAndFixturesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_f7c0398a-c122-4307-be2d-4f91a67fa85a" xlink:to="loc_us-gaap_FurnitureAndFixturesMember_1cff351a-0a43-45e4-8865-7e1f80c10bdd" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LeaseholdImprovementsMember_5d08afe2-a4f3-4645-8a37-14cf226084ae" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LeaseholdImprovementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_f7c0398a-c122-4307-be2d-4f91a67fa85a" xlink:to="loc_us-gaap_LeaseholdImprovementsMember_5d08afe2-a4f3-4645-8a37-14cf226084ae" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ToolsDiesAndMoldsMember_77bef24c-b5ad-4d5c-8ee0-14ff3a8f6e1f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ToolsDiesAndMoldsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_f7c0398a-c122-4307-be2d-4f91a67fa85a" xlink:to="loc_us-gaap_ToolsDiesAndMoldsMember_77bef24c-b5ad-4d5c-8ee0-14ff3a8f6e1f" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_b63c2549-0220-42af-a8d7-254c57ca826c" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_bf1785be-dc2e-479a-b846-152c84dfb63f" xlink:to="loc_srt_RangeAxis_b63c2549-0220-42af-a8d7-254c57ca826c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_b63c2549-0220-42af-a8d7-254c57ca826c_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_b63c2549-0220-42af-a8d7-254c57ca826c" xlink:to="loc_srt_RangeMember_b63c2549-0220-42af-a8d7-254c57ca826c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_7b9415ce-f3b1-4702-b66e-ffd1e39f2d97" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_b63c2549-0220-42af-a8d7-254c57ca826c" xlink:to="loc_srt_RangeMember_7b9415ce-f3b1-4702-b66e-ffd1e39f2d97" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_8086ac50-ebbc-4936-a21d-86ec5d7b9826" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_7b9415ce-f3b1-4702-b66e-ffd1e39f2d97" xlink:to="loc_srt_MinimumMember_8086ac50-ebbc-4936-a21d-86ec5d7b9826" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_5b5e58c3-38cb-42be-9328-b19d9164c6fb" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_7b9415ce-f3b1-4702-b66e-ffd1e39f2d97" xlink:to="loc_srt_MaximumMember_5b5e58c3-38cb-42be-9328-b19d9164c6fb" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://eosenergystorage.com/role/IntangibleAssetsNarrativesDetails" xlink:type="simple" xlink:href="eose-20220930.xsd#IntangibleAssetsNarrativesDetails"/>
  <link:definitionLink xlink:role="http://eosenergystorage.com/role/IntangibleAssetsNarrativesDetails" xlink:type="extended" id="ic23651026485415586b899a4784f4d4c_IntangibleAssetsNarrativesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_8516e7fb-354c-4614-8bdc-5ba5370a7575" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsGross_1784d2c8-dc69-4a37-bc29-9f4e36e5a1bf" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetsGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_8516e7fb-354c-4614-8bdc-5ba5370a7575" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsGross_1784d2c8-dc69-4a37-bc29-9f4e36e5a1bf" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_b0224586-45cd-4127-a634-5fb4fe7aa06f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetUsefulLife"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_8516e7fb-354c-4614-8bdc-5ba5370a7575" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_b0224586-45cd-4127-a634-5fb4fe7aa06f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfIntangibleAssets_196cda0e-555a-40d8-9132-87a2afcddeb9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AmortizationOfIntangibleAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_8516e7fb-354c-4614-8bdc-5ba5370a7575" xlink:to="loc_us-gaap_AmortizationOfIntangibleAssets_196cda0e-555a-40d8-9132-87a2afcddeb9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_e34243df-4ecd-4767-86d0-5e4b2342c64f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_8516e7fb-354c-4614-8bdc-5ba5370a7575" xlink:to="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_e34243df-4ecd-4767-86d0-5e4b2342c64f" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_f8516b22-b911-4f8c-93e4-933dd287e3ec" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_e34243df-4ecd-4767-86d0-5e4b2342c64f" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_f8516b22-b911-4f8c-93e4-933dd287e3ec" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_f8516b22-b911-4f8c-93e4-933dd287e3ec_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_f8516b22-b911-4f8c-93e4-933dd287e3ec" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_f8516b22-b911-4f8c-93e4-933dd287e3ec_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_8103c6ba-3321-46c7-a397-1d85f6f1daad" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_f8516b22-b911-4f8c-93e4-933dd287e3ec" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_8103c6ba-3321-46c7-a397-1d85f6f1daad" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PatentsMember_711da1b7-3afd-40a3-ba60-8fcda4797b51" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PatentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_8103c6ba-3321-46c7-a397-1d85f6f1daad" xlink:to="loc_us-gaap_PatentsMember_711da1b7-3afd-40a3-ba60-8fcda4797b51" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://eosenergystorage.com/role/NotesReceivableNetandVariableInterestEntitiesVIEsConsiderationDetails" xlink:type="simple" xlink:href="eose-20220930.xsd#NotesReceivableNetandVariableInterestEntitiesVIEsConsiderationDetails"/>
  <link:definitionLink xlink:role="http://eosenergystorage.com/role/NotesReceivableNetandVariableInterestEntitiesVIEsConsiderationDetails" xlink:type="extended" id="i72ad1b8c7d06433191ddfde27c4458f5_NotesReceivableNetandVariableInterestEntitiesVIEsConsiderationDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableInterestEntityLineItems_af7da124-fe8a-479d-add9-7fa621c49674" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_VariableInterestEntityLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NotesReceivableNet_95ce46ed-d7f8-44e4-a741-aa0f4b828fbe" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NotesReceivableNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_af7da124-fe8a-479d-add9-7fa621c49674" xlink:to="loc_us-gaap_NotesReceivableNet_95ce46ed-d7f8-44e4-a741-aa0f4b828fbe" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableAllowanceForCreditLosses_bda4cca5-d710-49ea-98d1-36f1461a3a2a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancingReceivableAllowanceForCreditLosses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_af7da124-fe8a-479d-add9-7fa621c49674" xlink:to="loc_us-gaap_FinancingReceivableAllowanceForCreditLosses_bda4cca5-d710-49ea-98d1-36f1461a3a2a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfVariableInterestEntitiesTable_c8a13cbd-dd57-47bd-9c84-90d2f0f2be58" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfVariableInterestEntitiesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_af7da124-fe8a-479d-add9-7fa621c49674" xlink:to="loc_us-gaap_ScheduleOfVariableInterestEntitiesTable_c8a13cbd-dd57-47bd-9c84-90d2f0f2be58" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_a6de2fb4-6db8-4576-bad7-34dd102f5942" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfVariableInterestEntitiesTable_c8a13cbd-dd57-47bd-9c84-90d2f0f2be58" xlink:to="loc_srt_ConsolidatedEntitiesAxis_a6de2fb4-6db8-4576-bad7-34dd102f5942" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_a6de2fb4-6db8-4576-bad7-34dd102f5942_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_a6de2fb4-6db8-4576-bad7-34dd102f5942" xlink:to="loc_srt_ConsolidatedEntitiesDomain_a6de2fb4-6db8-4576-bad7-34dd102f5942_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_e69b4854-e6b3-4095-9c16-da3d22fc4210" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_a6de2fb4-6db8-4576-bad7-34dd102f5942" xlink:to="loc_srt_ConsolidatedEntitiesDomain_e69b4854-e6b3-4095-9c16-da3d22fc4210" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableInterestEntityNotPrimaryBeneficiaryMember_a1f5c5a2-f47c-4202-a1c4-162a9528fe53" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_VariableInterestEntityNotPrimaryBeneficiaryMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_e69b4854-e6b3-4095-9c16-da3d22fc4210" xlink:to="loc_us-gaap_VariableInterestEntityNotPrimaryBeneficiaryMember_a1f5c5a2-f47c-4202-a1c4-162a9528fe53" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://eosenergystorage.com/role/RelatedPartyTransactionsDetails" xlink:type="simple" xlink:href="eose-20220930.xsd#RelatedPartyTransactionsDetails"/>
  <link:definitionLink xlink:role="http://eosenergystorage.com/role/RelatedPartyTransactionsDetails" xlink:type="extended" id="ia16c1d6a49ac4353ac72aa2697aebe9c_RelatedPartyTransactionsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_1f5b56d0-3c8d-4b81-9dc3-d5005d5f5f5b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RelatedPartyTransactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NotesReceivableRelatedParties_527f8e43-a1b6-4b56-a869-c66e47130d2a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NotesReceivableRelatedParties"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_1f5b56d0-3c8d-4b81-9dc3-d5005d5f5f5b" xlink:to="loc_us-gaap_NotesReceivableRelatedParties_527f8e43-a1b6-4b56-a869-c66e47130d2a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsOfDebtIssuanceCosts_b1dc89e3-f8fa-42e3-a8b4-c42da4b3e21f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PaymentsOfDebtIssuanceCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_1f5b56d0-3c8d-4b81-9dc3-d5005d5f5f5b" xlink:to="loc_us-gaap_PaymentsOfDebtIssuanceCosts_b1dc89e3-f8fa-42e3-a8b4-c42da4b3e21f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeneralAndAdministrativeExpense_a6219cbf-c16a-4140-b30f-15df53966adf" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_GeneralAndAdministrativeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_1f5b56d0-3c8d-4b81-9dc3-d5005d5f5f5b" xlink:to="loc_us-gaap_GeneralAndAdministrativeExpense_a6219cbf-c16a-4140-b30f-15df53966adf" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DueFromRelatedPartiesCurrent_a524a2ed-03ff-4167-a19a-f9dc5b607bbf" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DueFromRelatedPartiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_1f5b56d0-3c8d-4b81-9dc3-d5005d5f5f5b" xlink:to="loc_us-gaap_DueFromRelatedPartiesCurrent_a524a2ed-03ff-4167-a19a-f9dc5b607bbf" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_SaleOfStockAuthorizedAmountValue_84709e2d-5216-4aba-8fbe-d91306d4e1b2" xlink:href="eose-20220930.xsd#eose_SaleOfStockAuthorizedAmountValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_1f5b56d0-3c8d-4b81-9dc3-d5005d5f5f5b" xlink:to="loc_eose_SaleOfStockAuthorizedAmountValue_84709e2d-5216-4aba-8fbe-d91306d4e1b2" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockConsiderationReceivedPerTransaction_3197d785-bf75-4d60-b58c-30cd9daeeb72" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SaleOfStockConsiderationReceivedPerTransaction"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_1f5b56d0-3c8d-4b81-9dc3-d5005d5f5f5b" xlink:to="loc_us-gaap_SaleOfStockConsiderationReceivedPerTransaction_3197d785-bf75-4d60-b58c-30cd9daeeb72" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_SharePriceAsPercentageOfMarketPrice_08de7a4c-80e4-447c-8886-205bf03ef0d6" xlink:href="eose-20220930.xsd#eose_SharePriceAsPercentageOfMarketPrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_1f5b56d0-3c8d-4b81-9dc3-d5005d5f5f5b" xlink:to="loc_eose_SharePriceAsPercentageOfMarketPrice_08de7a4c-80e4-447c-8886-205bf03ef0d6" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockPercentageOfOwnershipAfterTransaction_dc7f8948-f9d6-43f4-96d0-59ba868fc21d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SaleOfStockPercentageOfOwnershipAfterTransaction"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_1f5b56d0-3c8d-4b81-9dc3-d5005d5f5f5b" xlink:to="loc_us-gaap_SaleOfStockPercentageOfOwnershipAfterTransaction_dc7f8948-f9d6-43f4-96d0-59ba868fc21d" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_SaleOfStockOwnershipThresholdAfterExchangeCapPercent_5d817c45-c2b7-4bd4-8486-f47fa743476b" xlink:href="eose-20220930.xsd#eose_SaleOfStockOwnershipThresholdAfterExchangeCapPercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_1f5b56d0-3c8d-4b81-9dc3-d5005d5f5f5b" xlink:to="loc_eose_SaleOfStockOwnershipThresholdAfterExchangeCapPercent_5d817c45-c2b7-4bd4-8486-f47fa743476b" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_NumberOfPreAdvanceLoans_f470b569-71a9-4749-bc74-9370441a587c" xlink:href="eose-20220930.xsd#eose_NumberOfPreAdvanceLoans"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_1f5b56d0-3c8d-4b81-9dc3-d5005d5f5f5b" xlink:to="loc_eose_NumberOfPreAdvanceLoans_f470b569-71a9-4749-bc74-9370441a587c" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_MaximumBorrowingCapacityPrincipalAmountPerLoan_5c77b4f5-e54d-405c-ab28-5610ba9d9b58" xlink:href="eose-20220930.xsd#eose_MaximumBorrowingCapacityPrincipalAmountPerLoan"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_1f5b56d0-3c8d-4b81-9dc3-d5005d5f5f5b" xlink:to="loc_eose_MaximumBorrowingCapacityPrincipalAmountPerLoan_5c77b4f5-e54d-405c-ab28-5610ba9d9b58" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_EquityInterestsIssuedOrIssuableNumberOfSharesIssued_1c92f293-f55f-4319-a752-22bae99179b1" xlink:href="eose-20220930.xsd#eose_EquityInterestsIssuedOrIssuableNumberOfSharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_1f5b56d0-3c8d-4b81-9dc3-d5005d5f5f5b" xlink:to="loc_eose_EquityInterestsIssuedOrIssuableNumberOfSharesIssued_1c92f293-f55f-4319-a752-22bae99179b1" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsInHedgesAssetsAtFairValue_d936ec89-dd3c-440a-9533-d9e3ae39c10e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeInstrumentsInHedgesAssetsAtFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_1f5b56d0-3c8d-4b81-9dc3-d5005d5f5f5b" xlink:to="loc_us-gaap_DerivativeInstrumentsInHedgesAssetsAtFairValue_d936ec89-dd3c-440a-9533-d9e3ae39c10e" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockConsiderationReceivedOnTransaction_0298207c-c00f-4822-9aae-49cf6a681678" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SaleOfStockConsiderationReceivedOnTransaction"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_1f5b56d0-3c8d-4b81-9dc3-d5005d5f5f5b" xlink:to="loc_us-gaap_SaleOfStockConsiderationReceivedOnTransaction_0298207c-c00f-4822-9aae-49cf6a681678" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction_8a1711a3-ee92-4b54-b5d3-5e9ede47d5a9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_1f5b56d0-3c8d-4b81-9dc3-d5005d5f5f5b" xlink:to="loc_us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction_8a1711a3-ee92-4b54-b5d3-5e9ede47d5a9" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_e713f5ad-7956-4566-9d36-b9ebd88c69b9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_1f5b56d0-3c8d-4b81-9dc3-d5005d5f5f5b" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_e713f5ad-7956-4566-9d36-b9ebd88c69b9" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtConversionConvertedInstrumentSharesIssued1_a48672d9-daa1-4799-b32d-0342bc2f52ed" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtConversionConvertedInstrumentSharesIssued1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_1f5b56d0-3c8d-4b81-9dc3-d5005d5f5f5b" xlink:to="loc_us-gaap_DebtConversionConvertedInstrumentSharesIssued1_a48672d9-daa1-4799-b32d-0342bc2f52ed" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_DebtConversionConvertedInstrumentConversionPricePerShare_dbc34b4f-c209-4850-9408-0a5bed34dc6f" xlink:href="eose-20220930.xsd#eose_DebtConversionConvertedInstrumentConversionPricePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_1f5b56d0-3c8d-4b81-9dc3-d5005d5f5f5b" xlink:to="loc_eose_DebtConversionConvertedInstrumentConversionPricePerShare_dbc34b4f-c209-4850-9408-0a5bed34dc6f" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtConversionConvertedInstrumentAmount1_a984d98e-900d-48cd-8aa0-629823c224ad" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtConversionConvertedInstrumentAmount1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_1f5b56d0-3c8d-4b81-9dc3-d5005d5f5f5b" xlink:to="loc_us-gaap_DebtConversionConvertedInstrumentAmount1_a984d98e-900d-48cd-8aa0-629823c224ad" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_5e619cac-77a2-496a-be15-f11505a2d812" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_1f5b56d0-3c8d-4b81-9dc3-d5005d5f5f5b" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_5e619cac-77a2-496a-be15-f11505a2d812" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CounterpartyNameAxis_d363c0c9-e364-47ec-b2ca-49310248c19d" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_CounterpartyNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_5e619cac-77a2-496a-be15-f11505a2d812" xlink:to="loc_srt_CounterpartyNameAxis_d363c0c9-e364-47ec-b2ca-49310248c19d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_d363c0c9-e364-47ec-b2ca-49310248c19d_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_d363c0c9-e364-47ec-b2ca-49310248c19d" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_d363c0c9-e364-47ec-b2ca-49310248c19d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_46a3e34d-468d-460e-afcc-420e93e8a648" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_d363c0c9-e364-47ec-b2ca-49310248c19d" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_46a3e34d-468d-460e-afcc-420e93e8a648" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_SpringCreekCapitalLLCMember_7a3da8b7-b5cb-4821-a867-60b298eebf02" xlink:href="eose-20220930.xsd#eose_SpringCreekCapitalLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_46a3e34d-468d-460e-afcc-420e93e8a648" xlink:to="loc_eose_SpringCreekCapitalLLCMember_7a3da8b7-b5cb-4821-a867-60b298eebf02" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_BRileySecuritiesIncMember_44ad75b8-eb97-459b-aebf-9876837cc518" xlink:href="eose-20220930.xsd#eose_BRileySecuritiesIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_46a3e34d-468d-460e-afcc-420e93e8a648" xlink:to="loc_eose_BRileySecuritiesIncMember_44ad75b8-eb97-459b-aebf-9876837cc518" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_HoltecInternationalMember_61588e09-4638-40a4-b90a-07c0ae2e8d1d" xlink:href="eose-20220930.xsd#eose_HoltecInternationalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_46a3e34d-468d-460e-afcc-420e93e8a648" xlink:to="loc_eose_HoltecInternationalMember_61588e09-4638-40a4-b90a-07c0ae2e8d1d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_02c577d0-93bf-4bba-ad14-ec3deb013414" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_5e619cac-77a2-496a-be15-f11505a2d812" xlink:to="loc_us-gaap_DebtInstrumentAxis_02c577d0-93bf-4bba-ad14-ec3deb013414" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_02c577d0-93bf-4bba-ad14-ec3deb013414_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_02c577d0-93bf-4bba-ad14-ec3deb013414" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_02c577d0-93bf-4bba-ad14-ec3deb013414_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_030f3b08-be71-4357-adc1-7dfccab9889f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_02c577d0-93bf-4bba-ad14-ec3deb013414" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_030f3b08-be71-4357-adc1-7dfccab9889f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_A2021ConvertibleNotesMember_787840d0-286c-4007-98fb-aab34c291724" xlink:href="eose-20220930.xsd#eose_A2021ConvertibleNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_030f3b08-be71-4357-adc1-7dfccab9889f" xlink:to="loc_eose_A2021ConvertibleNotesMember_787840d0-286c-4007-98fb-aab34c291724" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_YorkvilleConvertiblePromissoryNoteMember_82110e49-c2cb-4350-84d8-2c910d5c0322" xlink:href="eose-20220930.xsd#eose_YorkvilleConvertiblePromissoryNoteMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_030f3b08-be71-4357-adc1-7dfccab9889f" xlink:to="loc_eose_YorkvilleConvertiblePromissoryNoteMember_82110e49-c2cb-4350-84d8-2c910d5c0322" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_af16aaf2-00bc-4ade-b641-0ac86c58ee38" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_5e619cac-77a2-496a-be15-f11505a2d812" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_af16aaf2-00bc-4ade-b641-0ac86c58ee38" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_af16aaf2-00bc-4ade-b641-0ac86c58ee38_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_af16aaf2-00bc-4ade-b641-0ac86c58ee38" xlink:to="loc_us-gaap_RelatedPartyDomain_af16aaf2-00bc-4ade-b641-0ac86c58ee38_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_7d0a28f0-d71a-40a3-9d60-e069856b6ef7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_af16aaf2-00bc-4ade-b641-0ac86c58ee38" xlink:to="loc_us-gaap_RelatedPartyDomain_7d0a28f0-d71a-40a3-9d60-e069856b6ef7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvesteeMember_0240f68e-6c37-4432-84df-ba9c488e4755" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityMethodInvesteeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_7d0a28f0-d71a-40a3-9d60-e069856b6ef7" xlink:to="loc_us-gaap_EquityMethodInvesteeMember_0240f68e-6c37-4432-84df-ba9c488e4755" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_AffiliatedEntityMember_56be0f6d-329d-4262-a957-1ed4d370e9cb" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_AffiliatedEntityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_7d0a28f0-d71a-40a3-9d60-e069856b6ef7" xlink:to="loc_srt_AffiliatedEntityMember_56be0f6d-329d-4262-a957-1ed4d370e9cb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsidiarySaleOfStockAxis_103296ce-cbea-4652-8929-1bae23f04149" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SubsidiarySaleOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_5e619cac-77a2-496a-be15-f11505a2d812" xlink:to="loc_us-gaap_SubsidiarySaleOfStockAxis_103296ce-cbea-4652-8929-1bae23f04149" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_103296ce-cbea-4652-8929-1bae23f04149_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SaleOfStockNameOfTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_103296ce-cbea-4652-8929-1bae23f04149" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_103296ce-cbea-4652-8929-1bae23f04149_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_edb3f7a5-9c10-46b0-9d2a-4025e4e95046" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SaleOfStockNameOfTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_103296ce-cbea-4652-8929-1bae23f04149" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_edb3f7a5-9c10-46b0-9d2a-4025e4e95046" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrivatePlacementMember_ef7b5156-3faa-49b8-bd4b-1043b83f63e9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PrivatePlacementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SaleOfStockNameOfTransactionDomain_edb3f7a5-9c10-46b0-9d2a-4025e4e95046" xlink:to="loc_us-gaap_PrivatePlacementMember_ef7b5156-3faa-49b8-bd4b-1043b83f63e9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipAxis_dbb1727d-d53b-44ed-904f-cfc2849ae99b" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_OwnershipAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_5e619cac-77a2-496a-be15-f11505a2d812" xlink:to="loc_srt_OwnershipAxis_dbb1727d-d53b-44ed-904f-cfc2849ae99b" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipDomain_dbb1727d-d53b-44ed-904f-cfc2849ae99b_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_OwnershipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_OwnershipAxis_dbb1727d-d53b-44ed-904f-cfc2849ae99b" xlink:to="loc_srt_OwnershipDomain_dbb1727d-d53b-44ed-904f-cfc2849ae99b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipDomain_1e9ee37f-479a-4207-84cb-c8ad90be19d7" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_OwnershipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_OwnershipAxis_dbb1727d-d53b-44ed-904f-cfc2849ae99b" xlink:to="loc_srt_OwnershipDomain_1e9ee37f-479a-4207-84cb-c8ad90be19d7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_YorkvilleMember_2024c79d-c301-4f25-8fe3-7bc51c9e6f20" xlink:href="eose-20220930.xsd#eose_YorkvilleMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_OwnershipDomain_1e9ee37f-479a-4207-84cb-c8ad90be19d7" xlink:to="loc_eose_YorkvilleMember_2024c79d-c301-4f25-8fe3-7bc51c9e6f20" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_ece2abf9-6b0e-4618-9693-271fcf63d6f4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_5e619cac-77a2-496a-be15-f11505a2d812" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_ece2abf9-6b0e-4618-9693-271fcf63d6f4" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_ece2abf9-6b0e-4618-9693-271fcf63d6f4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_ece2abf9-6b0e-4618-9693-271fcf63d6f4" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_ece2abf9-6b0e-4618-9693-271fcf63d6f4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_14141f73-31c9-45e1-8afb-10659628d0d6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_ece2abf9-6b0e-4618-9693-271fcf63d6f4" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_14141f73-31c9-45e1-8afb-10659628d0d6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConvertibleDebtMember_0ecd8a71-b2dd-4a81-ac5f-c27bc01cadc3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ConvertibleDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_14141f73-31c9-45e1-8afb-10659628d0d6" xlink:to="loc_us-gaap_ConvertibleDebtMember_0ecd8a71-b2dd-4a81-ac5f-c27bc01cadc3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_42840e95-ae21-4d3c-bd38-d784d4a54448" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_5e619cac-77a2-496a-be15-f11505a2d812" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_42840e95-ae21-4d3c-bd38-d784d4a54448" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_42840e95-ae21-4d3c-bd38-d784d4a54448_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_42840e95-ae21-4d3c-bd38-d784d4a54448" xlink:to="loc_us-gaap_EquityComponentDomain_42840e95-ae21-4d3c-bd38-d784d4a54448_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_bfa76a80-0060-4ef4-ba8d-f42a8791b369" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_42840e95-ae21-4d3c-bd38-d784d4a54448" xlink:to="loc_us-gaap_EquityComponentDomain_bfa76a80-0060-4ef4-ba8d-f42a8791b369" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_2af0a885-f4cd-4b23-a0d5-10bbbd82fc72" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_bfa76a80-0060-4ef4-ba8d-f42a8791b369" xlink:to="loc_us-gaap_CommonStockMember_2af0a885-f4cd-4b23-a0d5-10bbbd82fc72" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://eosenergystorage.com/role/BorrowingsScheduleofDebtDetails" xlink:type="simple" xlink:href="eose-20220930.xsd#BorrowingsScheduleofDebtDetails"/>
  <link:definitionLink xlink:role="http://eosenergystorage.com/role/BorrowingsScheduleofDebtDetails" xlink:type="extended" id="i05c753b0cc634b5f83bd5496523d8d79_BorrowingsScheduleofDebtDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_448d4e94-7845-409d-8b3e-0a5de1123788" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_LongTermDebtGrossAbstract_b4f9346a-87f8-4331-8f9f-7c1b53c389dc" xlink:href="eose-20220930.xsd#eose_LongTermDebtGrossAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_448d4e94-7845-409d-8b3e-0a5de1123788" xlink:to="loc_eose_LongTermDebtGrossAbstract_b4f9346a-87f8-4331-8f9f-7c1b53c389dc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_NotesPayableRelatedPartiesGross_e5b67be8-26e0-4110-bb09-dfd14eca336b" xlink:href="eose-20220930.xsd#eose_NotesPayableRelatedPartiesGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_eose_LongTermDebtGrossAbstract_b4f9346a-87f8-4331-8f9f-7c1b53c389dc" xlink:to="loc_eose_NotesPayableRelatedPartiesGross_e5b67be8-26e0-4110-bb09-dfd14eca336b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_9c3c57f8-3a5a-4b6e-a86b-fb954808f251" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_eose_LongTermDebtGrossAbstract_b4f9346a-87f8-4331-8f9f-7c1b53c389dc" xlink:to="loc_us-gaap_DebtInstrumentCarryingAmount_9c3c57f8-3a5a-4b6e-a86b-fb954808f251" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_LongTermDebtGrossCurrentMaturities_ab0a8554-caf1-4d43-9e40-9fc1ba33dcf4" xlink:href="eose-20220930.xsd#eose_LongTermDebtGrossCurrentMaturities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_eose_LongTermDebtGrossAbstract_b4f9346a-87f8-4331-8f9f-7c1b53c389dc" xlink:to="loc_eose_LongTermDebtGrossCurrentMaturities_ab0a8554-caf1-4d43-9e40-9fc1ba33dcf4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_LongTermDebtGrossExcludingCurrentMaturities_ebb2ab4f-58a0-4387-84eb-5b1d0a9f1a5b" xlink:href="eose-20220930.xsd#eose_LongTermDebtGrossExcludingCurrentMaturities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_eose_LongTermDebtGrossAbstract_b4f9346a-87f8-4331-8f9f-7c1b53c389dc" xlink:to="loc_eose_LongTermDebtGrossExcludingCurrentMaturities_ebb2ab4f-58a0-4387-84eb-5b1d0a9f1a5b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtCurrentAndNoncurrentAbstract_969c97f6-5a44-4db3-aceb-5cfc917c2ec3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtCurrentAndNoncurrentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_448d4e94-7845-409d-8b3e-0a5de1123788" xlink:to="loc_us-gaap_LongtermDebtCurrentAndNoncurrentAbstract_969c97f6-5a44-4db3-aceb-5cfc917c2ec3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NotesPayableRelatedPartiesCurrentAndNoncurrent_7e187f17-39b3-4b06-9b0c-f77be53593c6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NotesPayableRelatedPartiesCurrentAndNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtCurrentAndNoncurrentAbstract_969c97f6-5a44-4db3-aceb-5cfc917c2ec3" xlink:to="loc_us-gaap_NotesPayableRelatedPartiesCurrentAndNoncurrent_7e187f17-39b3-4b06-9b0c-f77be53593c6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_def8a2d6-16f8-4443-8fcd-c9fe4ef1e640" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtCurrentAndNoncurrentAbstract_969c97f6-5a44-4db3-aceb-5cfc917c2ec3" xlink:to="loc_us-gaap_LongTermDebt_def8a2d6-16f8-4443-8fcd-c9fe4ef1e640" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtCurrent_cbc08e83-67c6-4c21-b211-f199ac18b530" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongTermDebtCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtCurrentAndNoncurrentAbstract_969c97f6-5a44-4db3-aceb-5cfc917c2ec3" xlink:to="loc_us-gaap_LongTermDebtCurrent_cbc08e83-67c6-4c21-b211-f199ac18b530" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtNoncurrent_febee18f-a18f-48f8-88c7-21d67fcc07ca" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongTermDebtNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtCurrentAndNoncurrentAbstract_969c97f6-5a44-4db3-aceb-5cfc917c2ec3" xlink:to="loc_us-gaap_LongTermDebtNoncurrent_febee18f-a18f-48f8-88c7-21d67fcc07ca" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_ac93b2bf-5e62-4e7d-a712-894fd239a98f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_448d4e94-7845-409d-8b3e-0a5de1123788" xlink:to="loc_us-gaap_DebtInstrumentTable_ac93b2bf-5e62-4e7d-a712-894fd239a98f" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_6427e9e7-fede-494d-b0c3-414c7095b6a0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_ac93b2bf-5e62-4e7d-a712-894fd239a98f" xlink:to="loc_us-gaap_DebtInstrumentAxis_6427e9e7-fede-494d-b0c3-414c7095b6a0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_6427e9e7-fede-494d-b0c3-414c7095b6a0_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_6427e9e7-fede-494d-b0c3-414c7095b6a0" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_6427e9e7-fede-494d-b0c3-414c7095b6a0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_11b4b4d3-de56-43e4-91d9-41d25478a25a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_6427e9e7-fede-494d-b0c3-414c7095b6a0" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_11b4b4d3-de56-43e4-91d9-41d25478a25a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_YorkvilleConvertiblePromissoryNoteMember_3404a0e8-5254-4b58-81b3-f95c499852bd" xlink:href="eose-20220930.xsd#eose_YorkvilleConvertiblePromissoryNoteMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_11b4b4d3-de56-43e4-91d9-41d25478a25a" xlink:to="loc_eose_YorkvilleConvertiblePromissoryNoteMember_3404a0e8-5254-4b58-81b3-f95c499852bd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_A2021ConvertibleNotesMember_a0422abf-31e7-40b7-b5db-9b9fba7569b9" xlink:href="eose-20220930.xsd#eose_A2021ConvertibleNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_11b4b4d3-de56-43e4-91d9-41d25478a25a" xlink:to="loc_eose_A2021ConvertibleNotesMember_a0422abf-31e7-40b7-b5db-9b9fba7569b9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_SeniorSecuredTermLoanAgreementMember_92ec5d9b-0f90-4581-a17f-550e5f2e72cd" xlink:href="eose-20220930.xsd#eose_SeniorSecuredTermLoanAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_11b4b4d3-de56-43e4-91d9-41d25478a25a" xlink:to="loc_eose_SeniorSecuredTermLoanAgreementMember_92ec5d9b-0f90-4581-a17f-550e5f2e72cd" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_EquipmentFinancingFacilityMember_8b5c64ff-7a7e-45d5-b8ff-236187f5f127" xlink:href="eose-20220930.xsd#eose_EquipmentFinancingFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_11b4b4d3-de56-43e4-91d9-41d25478a25a" xlink:to="loc_eose_EquipmentFinancingFacilityMember_8b5c64ff-7a7e-45d5-b8ff-236187f5f127" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_85a9acce-a275-4da8-b676-cc59f96070c6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_ac93b2bf-5e62-4e7d-a712-894fd239a98f" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_85a9acce-a275-4da8-b676-cc59f96070c6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_85a9acce-a275-4da8-b676-cc59f96070c6_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_85a9acce-a275-4da8-b676-cc59f96070c6" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_85a9acce-a275-4da8-b676-cc59f96070c6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_5bdd46ae-3462-4cc5-93ae-9f521989632a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_85a9acce-a275-4da8-b676-cc59f96070c6" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_5bdd46ae-3462-4cc5-93ae-9f521989632a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConvertibleDebtMember_139a0b48-8be4-4280-8ba9-56d446d6aa08" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ConvertibleDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_5bdd46ae-3462-4cc5-93ae-9f521989632a" xlink:to="loc_us-gaap_ConvertibleDebtMember_139a0b48-8be4-4280-8ba9-56d446d6aa08" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebtMember_e740fe6c-4986-45c9-9780-7c193d345610" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_5bdd46ae-3462-4cc5-93ae-9f521989632a" xlink:to="loc_us-gaap_SecuredDebtMember_e740fe6c-4986-45c9-9780-7c193d345610" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_1852e0f9-52d6-44b4-80e7-6924cc900e66" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_5bdd46ae-3462-4cc5-93ae-9f521989632a" xlink:to="loc_us-gaap_LineOfCreditMember_1852e0f9-52d6-44b4-80e7-6924cc900e66" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://eosenergystorage.com/role/BorrowingsNarrativeDetails" xlink:type="simple" xlink:href="eose-20220930.xsd#BorrowingsNarrativeDetails"/>
  <link:definitionLink xlink:role="http://eosenergystorage.com/role/BorrowingsNarrativeDetails" xlink:type="extended" id="iae93b771d2b2414b8c94df989947394b_BorrowingsNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_79922dad-1f8f-49d6-9412-3feb523d9b2c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_0b556950-3b7e-43c1-a0de-ccaad4284471" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_79922dad-1f8f-49d6-9412-3feb523d9b2c" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_0b556950-3b7e-43c1-a0de-ccaad4284471" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_DebtInstrumentDiscountRatePercentage_9b9d1889-332c-4996-866e-4eb007759f10" xlink:href="eose-20220930.xsd#eose_DebtInstrumentDiscountRatePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_79922dad-1f8f-49d6-9412-3feb523d9b2c" xlink:to="loc_eose_DebtInstrumentDiscountRatePercentage_9b9d1889-332c-4996-866e-4eb007759f10" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentConvertibleConversionPrice1_e684f5a9-ff35-4afa-a837-7a39890a78f0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentConvertibleConversionPrice1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_79922dad-1f8f-49d6-9412-3feb523d9b2c" xlink:to="loc_us-gaap_DebtInstrumentConvertibleConversionPrice1_e684f5a9-ff35-4afa-a837-7a39890a78f0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsOfDebtIssuanceCosts_ce31bcce-e662-436f-9b55-7e6da84f532a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PaymentsOfDebtIssuanceCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_79922dad-1f8f-49d6-9412-3feb523d9b2c" xlink:to="loc_us-gaap_PaymentsOfDebtIssuanceCosts_ce31bcce-e662-436f-9b55-7e6da84f532a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpense_b84dd71f-bdb5-4861-8790-8495c605ca5a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InterestExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_79922dad-1f8f-49d6-9412-3feb523d9b2c" xlink:to="loc_us-gaap_InterestExpense_b84dd71f-bdb5-4861-8790-8495c605ca5a" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_NumberOfInvestorNoticesDelivered_10a62d8c-bad5-4bc4-b9b7-09398313661a" xlink:href="eose-20220930.xsd#eose_NumberOfInvestorNoticesDelivered"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_79922dad-1f8f-49d6-9412-3feb523d9b2c" xlink:to="loc_eose_NumberOfInvestorNoticesDelivered_10a62d8c-bad5-4bc4-b9b7-09398313661a" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtConversionConvertedInstrumentSharesIssued1_78916805-f87e-4937-aaeb-8a677b146c37" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtConversionConvertedInstrumentSharesIssued1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_79922dad-1f8f-49d6-9412-3feb523d9b2c" xlink:to="loc_us-gaap_DebtConversionConvertedInstrumentSharesIssued1_78916805-f87e-4937-aaeb-8a677b146c37" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_DebtConversionConvertedInstrumentConversionPricePerShare_2abcde9e-d655-4f6a-a89c-b75caae7a7f9" xlink:href="eose-20220930.xsd#eose_DebtConversionConvertedInstrumentConversionPricePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_79922dad-1f8f-49d6-9412-3feb523d9b2c" xlink:to="loc_eose_DebtConversionConvertedInstrumentConversionPricePerShare_2abcde9e-d655-4f6a-a89c-b75caae7a7f9" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_30f913c0-f418-4c53-b490-1d852dc9903e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_79922dad-1f8f-49d6-9412-3feb523d9b2c" xlink:to="loc_us-gaap_DebtInstrumentCarryingAmount_30f913c0-f418-4c53-b490-1d852dc9903e" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmbeddedDerivativeFairValueOfEmbeddedDerivativeLiability_49c2bebd-0015-4224-ad8c-da7fbd2ea7a0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EmbeddedDerivativeFairValueOfEmbeddedDerivativeLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_79922dad-1f8f-49d6-9412-3feb523d9b2c" xlink:to="loc_us-gaap_EmbeddedDerivativeFairValueOfEmbeddedDerivativeLiability_49c2bebd-0015-4224-ad8c-da7fbd2ea7a0" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_DebtInstrumentConvertibleGainLossOnBeneficialConversionFeature_c717f83f-ca18-40ee-94b0-fc5b0d16c3de" xlink:href="eose-20220930.xsd#eose_DebtInstrumentConvertibleGainLossOnBeneficialConversionFeature"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_79922dad-1f8f-49d6-9412-3feb523d9b2c" xlink:to="loc_eose_DebtInstrumentConvertibleGainLossOnBeneficialConversionFeature_c717f83f-ca18-40ee-94b0-fc5b0d16c3de" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaidInKindInterest_4208c682-730e-4ff0-a927-bc80269deeed" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PaidInKindInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_79922dad-1f8f-49d6-9412-3feb523d9b2c" xlink:to="loc_us-gaap_PaidInKindInterest_4208c682-730e-4ff0-a927-bc80269deeed" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_InterestPayableRelatedPartyNoncurrent_83fb2d19-4bb8-4b4e-a8a6-b55e4e56c150" xlink:href="eose-20220930.xsd#eose_InterestPayableRelatedPartyNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_79922dad-1f8f-49d6-9412-3feb523d9b2c" xlink:to="loc_eose_InterestPayableRelatedPartyNoncurrent_83fb2d19-4bb8-4b4e-a8a6-b55e4e56c150" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromIssuanceOfSecuredDebt_ccca1782-19cb-4734-8247-9d4733820d03" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ProceedsFromIssuanceOfSecuredDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_79922dad-1f8f-49d6-9412-3feb523d9b2c" xlink:to="loc_us-gaap_ProceedsFromIssuanceOfSecuredDebt_ccca1782-19cb-4734-8247-9d4733820d03" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_DebtIntrumentMaturityNumberOfDaysPriorToCurrentMaturityDate_5619f6d8-c315-4129-9e4f-34a363be4963" xlink:href="eose-20220930.xsd#eose_DebtIntrumentMaturityNumberOfDaysPriorToCurrentMaturityDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_79922dad-1f8f-49d6-9412-3feb523d9b2c" xlink:to="loc_eose_DebtIntrumentMaturityNumberOfDaysPriorToCurrentMaturityDate_5619f6d8-c315-4129-9e4f-34a363be4963" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_DebtInstrumentMinimumPrepaymentAmount_2e71b0aa-3409-488e-a173-289de4cb342e" xlink:href="eose-20220930.xsd#eose_DebtInstrumentMinimumPrepaymentAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_79922dad-1f8f-49d6-9412-3feb523d9b2c" xlink:to="loc_eose_DebtInstrumentMinimumPrepaymentAmount_2e71b0aa-3409-488e-a173-289de4cb342e" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_f37f01ec-f2dc-490f-b694-39b3e1fa58b3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_79922dad-1f8f-49d6-9412-3feb523d9b2c" xlink:to="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_f37f01ec-f2dc-490f-b694-39b3e1fa58b3" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_021466b4-a960-4603-bf3d-6cc4eb9f0514" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_79922dad-1f8f-49d6-9412-3feb523d9b2c" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_021466b4-a960-4603-bf3d-6cc4eb9f0514" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateEffectivePercentage_637f83ef-9a43-4d4c-a4c9-cb82ebb2a917" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentInterestRateEffectivePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_79922dad-1f8f-49d6-9412-3feb523d9b2c" xlink:to="loc_us-gaap_DebtInstrumentInterestRateEffectivePercentage_637f83ef-9a43-4d4c-a4c9-cb82ebb2a917" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredFinanceCostsGross_b4a76a31-4751-4e73-accd-d6440ea157b0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DeferredFinanceCostsGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_79922dad-1f8f-49d6-9412-3feb523d9b2c" xlink:to="loc_us-gaap_DeferredFinanceCostsGross_b4a76a31-4751-4e73-accd-d6440ea157b0" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtIssuanceCostsLineOfCreditArrangementsGross_78043f83-796f-4c3c-b681-11d2b7287762" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtIssuanceCostsLineOfCreditArrangementsGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_79922dad-1f8f-49d6-9412-3feb523d9b2c" xlink:to="loc_us-gaap_DebtIssuanceCostsLineOfCreditArrangementsGross_78043f83-796f-4c3c-b681-11d2b7287762" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_DebtIssuanceCostInsurancePremiumsAmount_bfc13944-6059-4082-85a2-56b13fb30d46" xlink:href="eose-20220930.xsd#eose_DebtIssuanceCostInsurancePremiumsAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_79922dad-1f8f-49d6-9412-3feb523d9b2c" xlink:to="loc_eose_DebtIssuanceCostInsurancePremiumsAmount_bfc13944-6059-4082-85a2-56b13fb30d46" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_DebtInstrumentAdditionalPremiumPercentageToBePaid_fc1cd191-d483-412b-9804-b52d78da0103" xlink:href="eose-20220930.xsd#eose_DebtInstrumentAdditionalPremiumPercentageToBePaid"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_79922dad-1f8f-49d6-9412-3feb523d9b2c" xlink:to="loc_eose_DebtInstrumentAdditionalPremiumPercentageToBePaid_fc1cd191-d483-412b-9804-b52d78da0103" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccruedInsuranceCurrentAndNoncurrent_fde1c608-4f4a-4c78-94f7-6cc8b17c2919" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccruedInsuranceCurrentAndNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_79922dad-1f8f-49d6-9412-3feb523d9b2c" xlink:to="loc_us-gaap_AccruedInsuranceCurrentAndNoncurrent_fde1c608-4f4a-4c78-94f7-6cc8b17c2919" xlink:type="arc" order="23"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_NumberOfImmediatelyFollowingInterestPaymentRequiredToBeEscrowed_14a15571-075e-4361-8c02-af416eae7838" xlink:href="eose-20220930.xsd#eose_NumberOfImmediatelyFollowingInterestPaymentRequiredToBeEscrowed"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_79922dad-1f8f-49d6-9412-3feb523d9b2c" xlink:to="loc_eose_NumberOfImmediatelyFollowingInterestPaymentRequiredToBeEscrowed_14a15571-075e-4361-8c02-af416eae7838" xlink:type="arc" order="24"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EscrowDeposit_fa2ceab0-0818-47b5-a71e-3552645b4d96" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EscrowDeposit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_79922dad-1f8f-49d6-9412-3feb523d9b2c" xlink:to="loc_us-gaap_EscrowDeposit_fa2ceab0-0818-47b5-a71e-3552645b4d96" xlink:type="arc" order="25"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_MaximumBorrowingCapacityPrincipalAmountPerLoan_ff54b848-dd06-45d8-ab66-a77222b5fdf9" xlink:href="eose-20220930.xsd#eose_MaximumBorrowingCapacityPrincipalAmountPerLoan"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_79922dad-1f8f-49d6-9412-3feb523d9b2c" xlink:to="loc_eose_MaximumBorrowingCapacityPrincipalAmountPerLoan_ff54b848-dd06-45d8-ab66-a77222b5fdf9" xlink:type="arc" order="26"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_6a4575e0-cc88-43b6-8e49-c918f12b7b95" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_79922dad-1f8f-49d6-9412-3feb523d9b2c" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_6a4575e0-cc88-43b6-8e49-c918f12b7b95" xlink:type="arc" order="27"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromLongTermLinesOfCredit_9048aec8-344a-41cc-b0f0-9d12f459af94" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ProceedsFromLongTermLinesOfCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_79922dad-1f8f-49d6-9412-3feb523d9b2c" xlink:to="loc_us-gaap_ProceedsFromLongTermLinesOfCredit_9048aec8-344a-41cc-b0f0-9d12f459af94" xlink:type="arc" order="28"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityCommitmentFeeAmount_ed5f2e76-339a-4891-9cbd-103ff2cc2cbf" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LineOfCreditFacilityCommitmentFeeAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_79922dad-1f8f-49d6-9412-3feb523d9b2c" xlink:to="loc_us-gaap_LineOfCreditFacilityCommitmentFeeAmount_ed5f2e76-339a-4891-9cbd-103ff2cc2cbf" xlink:type="arc" order="29"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity_c4467f4d-d116-4790-bb49-3654dd2d1115" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_79922dad-1f8f-49d6-9412-3feb523d9b2c" xlink:to="loc_us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity_c4467f4d-d116-4790-bb49-3654dd2d1115" xlink:type="arc" order="30"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCredit_374fe07d-6516-4dc6-970f-2fa66aacf92f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LineOfCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_79922dad-1f8f-49d6-9412-3feb523d9b2c" xlink:to="loc_us-gaap_LineOfCredit_374fe07d-6516-4dc6-970f-2fa66aacf92f" xlink:type="arc" order="31"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LinesOfCreditCurrent_d964ad6e-4413-4b0f-91b0-04f64afa7075" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LinesOfCreditCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_79922dad-1f8f-49d6-9412-3feb523d9b2c" xlink:to="loc_us-gaap_LinesOfCreditCurrent_d964ad6e-4413-4b0f-91b0-04f64afa7075" xlink:type="arc" order="32"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseDebt_11dd33d1-505d-4bf3-973c-543bd1e1026d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InterestExpenseDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_79922dad-1f8f-49d6-9412-3feb523d9b2c" xlink:to="loc_us-gaap_InterestExpenseDebt_11dd33d1-505d-4bf3-973c-543bd1e1026d" xlink:type="arc" order="33"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferred1_8ccbc066-855a-4b8c-9bb9-182ae03778dd" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessCombinationConsiderationTransferred1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_79922dad-1f8f-49d6-9412-3feb523d9b2c" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferred1_8ccbc066-855a-4b8c-9bb9-182ae03778dd" xlink:type="arc" order="34"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesGross_e20d3341-3eb6-40b7-9ba4-f8891cfce4d2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PaymentsToAcquireBusinessesGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_79922dad-1f8f-49d6-9412-3feb523d9b2c" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesGross_e20d3341-3eb6-40b7-9ba4-f8891cfce4d2" xlink:type="arc" order="35"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNotesPayableCurrent_2dadd2e0-240e-415e-840f-b8545c6effb5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherNotesPayableCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_79922dad-1f8f-49d6-9412-3feb523d9b2c" xlink:to="loc_us-gaap_OtherNotesPayableCurrent_2dadd2e0-240e-415e-840f-b8545c6effb5" xlink:type="arc" order="36"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLongTermNotesPayable_6dafedba-8229-4590-b979-eeb775abab56" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherLongTermNotesPayable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_79922dad-1f8f-49d6-9412-3feb523d9b2c" xlink:to="loc_us-gaap_OtherLongTermNotesPayable_6dafedba-8229-4590-b979-eeb775abab56" xlink:type="arc" order="37"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainsLossesOnExtinguishmentOfDebt_f440cb79-79a1-48ae-9882-2a3bf5f02617" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_GainsLossesOnExtinguishmentOfDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_79922dad-1f8f-49d6-9412-3feb523d9b2c" xlink:to="loc_us-gaap_GainsLossesOnExtinguishmentOfDebt_f440cb79-79a1-48ae-9882-2a3bf5f02617" xlink:type="arc" order="38"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_0c5ddc9d-abf2-4675-ae6a-f79f9e00f706" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_79922dad-1f8f-49d6-9412-3feb523d9b2c" xlink:to="loc_us-gaap_DebtInstrumentTable_0c5ddc9d-abf2-4675-ae6a-f79f9e00f706" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_8fe202a0-6fc9-477d-90f2-f0a312fb1764" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_0c5ddc9d-abf2-4675-ae6a-f79f9e00f706" xlink:to="loc_us-gaap_DebtInstrumentAxis_8fe202a0-6fc9-477d-90f2-f0a312fb1764" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_8fe202a0-6fc9-477d-90f2-f0a312fb1764_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_8fe202a0-6fc9-477d-90f2-f0a312fb1764" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_8fe202a0-6fc9-477d-90f2-f0a312fb1764_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_fea99165-54a9-4ae1-ac26-7f02e09d2d4e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_8fe202a0-6fc9-477d-90f2-f0a312fb1764" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_fea99165-54a9-4ae1-ac26-7f02e09d2d4e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_YorkvilleConvertiblePromissoryNoteMember_cfd717de-128d-4517-8dd2-cb8419e7d34d" xlink:href="eose-20220930.xsd#eose_YorkvilleConvertiblePromissoryNoteMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_fea99165-54a9-4ae1-ac26-7f02e09d2d4e" xlink:to="loc_eose_YorkvilleConvertiblePromissoryNoteMember_cfd717de-128d-4517-8dd2-cb8419e7d34d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_A2021ConvertibleNotesMember_0b70b529-c090-49c6-8670-8388ef4fedd5" xlink:href="eose-20220930.xsd#eose_A2021ConvertibleNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_fea99165-54a9-4ae1-ac26-7f02e09d2d4e" xlink:to="loc_eose_A2021ConvertibleNotesMember_0b70b529-c090-49c6-8670-8388ef4fedd5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_SeniorSecuredTermLoanAgreementMember_0ef223cd-061d-4a05-bf3e-9137698ab6fe" xlink:href="eose-20220930.xsd#eose_SeniorSecuredTermLoanAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_fea99165-54a9-4ae1-ac26-7f02e09d2d4e" xlink:to="loc_eose_SeniorSecuredTermLoanAgreementMember_0ef223cd-061d-4a05-bf3e-9137698ab6fe" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_EquipmentFinancingFacilityMember_6abce326-9580-47a1-8f34-2426b51ff06a" xlink:href="eose-20220930.xsd#eose_EquipmentFinancingFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_fea99165-54a9-4ae1-ac26-7f02e09d2d4e" xlink:to="loc_eose_EquipmentFinancingFacilityMember_6abce326-9580-47a1-8f34-2426b51ff06a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_HiPowerPurchaseAgreementMember_fe49e936-dbc3-4539-97c1-9f7c039ebe3f" xlink:href="eose-20220930.xsd#eose_HiPowerPurchaseAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_fea99165-54a9-4ae1-ac26-7f02e09d2d4e" xlink:to="loc_eose_HiPowerPurchaseAgreementMember_fe49e936-dbc3-4539-97c1-9f7c039ebe3f" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_856ec12e-831d-440e-b93f-f2cb2e319fad" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_0c5ddc9d-abf2-4675-ae6a-f79f9e00f706" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_856ec12e-831d-440e-b93f-f2cb2e319fad" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_856ec12e-831d-440e-b93f-f2cb2e319fad_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_856ec12e-831d-440e-b93f-f2cb2e319fad" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_856ec12e-831d-440e-b93f-f2cb2e319fad_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_affe4f11-c2c3-4a3c-8d81-4824b08f8520" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_856ec12e-831d-440e-b93f-f2cb2e319fad" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_affe4f11-c2c3-4a3c-8d81-4824b08f8520" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConvertibleDebtMember_aaf7670d-e663-4ea6-8577-31e5492be42c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ConvertibleDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_affe4f11-c2c3-4a3c-8d81-4824b08f8520" xlink:to="loc_us-gaap_ConvertibleDebtMember_aaf7670d-e663-4ea6-8577-31e5492be42c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebtMember_2d8e65f8-2bb1-4351-894d-ef892e0d8bf9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_affe4f11-c2c3-4a3c-8d81-4824b08f8520" xlink:to="loc_us-gaap_SecuredDebtMember_2d8e65f8-2bb1-4351-894d-ef892e0d8bf9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_SOFRLoansMember_76a74e87-8d52-41c6-b72f-67de92481582" xlink:href="eose-20220930.xsd#eose_SOFRLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SecuredDebtMember_2d8e65f8-2bb1-4351-894d-ef892e0d8bf9" xlink:to="loc_eose_SOFRLoansMember_76a74e87-8d52-41c6-b72f-67de92481582" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_ABRLoansMember_f2d9a9b4-d7ac-4f56-8c85-5256e937f93d" xlink:href="eose-20220930.xsd#eose_ABRLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SecuredDebtMember_2d8e65f8-2bb1-4351-894d-ef892e0d8bf9" xlink:to="loc_eose_ABRLoansMember_f2d9a9b4-d7ac-4f56-8c85-5256e937f93d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_e2765efb-3ad5-4b68-b556-8601d077bcb3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_affe4f11-c2c3-4a3c-8d81-4824b08f8520" xlink:to="loc_us-gaap_LineOfCreditMember_e2765efb-3ad5-4b68-b556-8601d077bcb3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NotesPayableOtherPayablesMember_d4ea78ec-be1d-4e31-aa71-5fa17c630bb0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NotesPayableOtherPayablesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_affe4f11-c2c3-4a3c-8d81-4824b08f8520" xlink:to="loc_us-gaap_NotesPayableOtherPayablesMember_d4ea78ec-be1d-4e31-aa71-5fa17c630bb0" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateAxis_5be55f02-cdc4-42a5-82bf-0f40055f1ae3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_VariableRateAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_0c5ddc9d-abf2-4675-ae6a-f79f9e00f706" xlink:to="loc_us-gaap_VariableRateAxis_5be55f02-cdc4-42a5-82bf-0f40055f1ae3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_5be55f02-cdc4-42a5-82bf-0f40055f1ae3_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_VariableRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VariableRateAxis_5be55f02-cdc4-42a5-82bf-0f40055f1ae3" xlink:to="loc_us-gaap_VariableRateDomain_5be55f02-cdc4-42a5-82bf-0f40055f1ae3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_c71c597e-bf44-4579-924e-a9e56d2d5cb8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_VariableRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VariableRateAxis_5be55f02-cdc4-42a5-82bf-0f40055f1ae3" xlink:to="loc_us-gaap_VariableRateDomain_c71c597e-bf44-4579-924e-a9e56d2d5cb8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_SecuredOvernightFinancingRateSOFRMember_6812508a-38be-4c51-9d3e-bb73dabe3018" xlink:href="eose-20220930.xsd#eose_SecuredOvernightFinancingRateSOFRMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_c71c597e-bf44-4579-924e-a9e56d2d5cb8" xlink:to="loc_eose_SecuredOvernightFinancingRateSOFRMember_6812508a-38be-4c51-9d3e-bb73dabe3018" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_FederalReserveBankOfNewYorkFinancingRateNYFRBMember_f1d771aa-78a7-4343-bf79-6b26cb13237f" xlink:href="eose-20220930.xsd#eose_FederalReserveBankOfNewYorkFinancingRateNYFRBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_c71c597e-bf44-4579-924e-a9e56d2d5cb8" xlink:to="loc_eose_FederalReserveBankOfNewYorkFinancingRateNYFRBMember_f1d771aa-78a7-4343-bf79-6b26cb13237f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_29ca2b93-9319-4ef8-b1a5-fb05c2b190bd" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentRedemptionPeriodAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_0c5ddc9d-abf2-4675-ae6a-f79f9e00f706" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_29ca2b93-9319-4ef8-b1a5-fb05c2b190bd" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_29ca2b93-9319-4ef8-b1a5-fb05c2b190bd_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentRedemptionPeriodDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_29ca2b93-9319-4ef8-b1a5-fb05c2b190bd" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_29ca2b93-9319-4ef8-b1a5-fb05c2b190bd_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_95086391-ce2a-46d6-bbcf-b26ffddf1352" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentRedemptionPeriodDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_29ca2b93-9319-4ef8-b1a5-fb05c2b190bd" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_95086391-ce2a-46d6-bbcf-b26ffddf1352" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodOneMember_2c42e801-bf19-4182-98c0-4e3a2c268f48" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentRedemptionPeriodOneMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_95086391-ce2a-46d6-bbcf-b26ffddf1352" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodOneMember_2c42e801-bf19-4182-98c0-4e3a2c268f48" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodTwoMember_af04a05c-e4f3-4262-a177-11505e3a9b9c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentRedemptionPeriodTwoMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_95086391-ce2a-46d6-bbcf-b26ffddf1352" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodTwoMember_af04a05c-e4f3-4262-a177-11505e3a9b9c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodThreeMember_eaf09eb9-e717-4713-a90c-481381e5af10" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentRedemptionPeriodThreeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_95086391-ce2a-46d6-bbcf-b26ffddf1352" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodThreeMember_eaf09eb9-e717-4713-a90c-481381e5af10" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_d38c81e1-4105-4238-ba2e-045e833e9602" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_0c5ddc9d-abf2-4675-ae6a-f79f9e00f706" xlink:to="loc_srt_RangeAxis_d38c81e1-4105-4238-ba2e-045e833e9602" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_d38c81e1-4105-4238-ba2e-045e833e9602_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_d38c81e1-4105-4238-ba2e-045e833e9602" xlink:to="loc_srt_RangeMember_d38c81e1-4105-4238-ba2e-045e833e9602_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_7d339697-2599-4a3d-80f2-c7c55ff45ce0" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_d38c81e1-4105-4238-ba2e-045e833e9602" xlink:to="loc_srt_RangeMember_7d339697-2599-4a3d-80f2-c7c55ff45ce0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_c6c0b0d2-2abe-451c-8832-0f9a68b29a17" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_7d339697-2599-4a3d-80f2-c7c55ff45ce0" xlink:to="loc_srt_MinimumMember_c6c0b0d2-2abe-451c-8832-0f9a68b29a17" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_17ca0b51-c859-453b-9573-0e35b6866fec" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_7d339697-2599-4a3d-80f2-c7c55ff45ce0" xlink:to="loc_srt_MaximumMember_17ca0b51-c859-453b-9573-0e35b6866fec" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_27e54317-c4d8-4cef-b64f-a0f9d55ec40f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_0c5ddc9d-abf2-4675-ae6a-f79f9e00f706" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_27e54317-c4d8-4cef-b64f-a0f9d55ec40f" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_27e54317-c4d8-4cef-b64f-a0f9d55ec40f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_27e54317-c4d8-4cef-b64f-a0f9d55ec40f" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_27e54317-c4d8-4cef-b64f-a0f9d55ec40f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_258d3eb7-11af-49c6-9dfa-bbec55b706db" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_27e54317-c4d8-4cef-b64f-a0f9d55ec40f" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_258d3eb7-11af-49c6-9dfa-bbec55b706db" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_HIPOWERLLCMember_b25e5f7b-b3b3-45d1-be6a-3e5adea3da3d" xlink:href="eose-20220930.xsd#eose_HIPOWERLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_258d3eb7-11af-49c6-9dfa-bbec55b706db" xlink:to="loc_eose_HIPOWERLLCMember_b25e5f7b-b3b3-45d1-be6a-3e5adea3da3d" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://eosenergystorage.com/role/BorrowingsDebtAssumptionsDetails" xlink:type="simple" xlink:href="eose-20220930.xsd#BorrowingsDebtAssumptionsDetails"/>
  <link:definitionLink xlink:role="http://eosenergystorage.com/role/BorrowingsDebtAssumptionsDetails" xlink:type="extended" id="id9d9c6c0c4524b69ad82df655f270c99_BorrowingsDebtAssumptionsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_e8c66651-397e-44b1-9b1f-e8359bcf67be" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTerm_167989ea-2643-44df-adb1-dd593f8ac0ad" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_e8c66651-397e-44b1-9b1f-e8359bcf67be" xlink:to="loc_us-gaap_DebtInstrumentTerm_167989ea-2643-44df-adb1-dd593f8ac0ad" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentMeasurementInput_89df7965-ee3d-46df-a55f-a911eefdda6a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentMeasurementInput"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_e8c66651-397e-44b1-9b1f-e8359bcf67be" xlink:to="loc_us-gaap_DebtInstrumentMeasurementInput_89df7965-ee3d-46df-a55f-a911eefdda6a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateEffectivePercentage_6c3264d1-b3df-412a-8754-69a81d86f970" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentInterestRateEffectivePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_e8c66651-397e-44b1-9b1f-e8359bcf67be" xlink:to="loc_us-gaap_DebtInstrumentInterestRateEffectivePercentage_6c3264d1-b3df-412a-8754-69a81d86f970" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_e4714b56-2132-4e84-9d47-01b9f5c95502" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_e8c66651-397e-44b1-9b1f-e8359bcf67be" xlink:to="loc_us-gaap_DebtInstrumentTable_e4714b56-2132-4e84-9d47-01b9f5c95502" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_8aa477b7-c44e-41af-ae68-a4787fa0f520" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_e4714b56-2132-4e84-9d47-01b9f5c95502" xlink:to="loc_us-gaap_DebtInstrumentAxis_8aa477b7-c44e-41af-ae68-a4787fa0f520" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_8aa477b7-c44e-41af-ae68-a4787fa0f520_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_8aa477b7-c44e-41af-ae68-a4787fa0f520" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_8aa477b7-c44e-41af-ae68-a4787fa0f520_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_19850059-de3c-48b9-918a-f24ffb8458ad" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_8aa477b7-c44e-41af-ae68-a4787fa0f520" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_19850059-de3c-48b9-918a-f24ffb8458ad" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_A2021ConvertibleNotesMember_6d2f0869-621c-4d97-88c9-a17ed230012c" xlink:href="eose-20220930.xsd#eose_A2021ConvertibleNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_19850059-de3c-48b9-918a-f24ffb8458ad" xlink:to="loc_eose_A2021ConvertibleNotesMember_6d2f0869-621c-4d97-88c9-a17ed230012c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputTypeAxis_1d59c096-262f-4e00-9882-094769e26708" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_MeasurementInputTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_e4714b56-2132-4e84-9d47-01b9f5c95502" xlink:to="loc_us-gaap_MeasurementInputTypeAxis_1d59c096-262f-4e00-9882-094769e26708" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputTypeDomain_1d59c096-262f-4e00-9882-094769e26708_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_MeasurementInputTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_MeasurementInputTypeAxis_1d59c096-262f-4e00-9882-094769e26708" xlink:to="loc_us-gaap_MeasurementInputTypeDomain_1d59c096-262f-4e00-9882-094769e26708_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputTypeDomain_b0abf042-6323-4536-8992-69c8ee906564" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_MeasurementInputTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_MeasurementInputTypeAxis_1d59c096-262f-4e00-9882-094769e26708" xlink:to="loc_us-gaap_MeasurementInputTypeDomain_b0abf042-6323-4536-8992-69c8ee906564" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputExpectedDividendRateMember_db21674e-8375-4d69-9e09-aedfe882a943" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_MeasurementInputExpectedDividendRateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_b0abf042-6323-4536-8992-69c8ee906564" xlink:to="loc_us-gaap_MeasurementInputExpectedDividendRateMember_db21674e-8375-4d69-9e09-aedfe882a943" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputRiskFreeInterestRateMember_6abc0631-178a-4ad3-b5a3-306d4bbf51b5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_MeasurementInputRiskFreeInterestRateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_b0abf042-6323-4536-8992-69c8ee906564" xlink:to="loc_us-gaap_MeasurementInputRiskFreeInterestRateMember_6abc0631-178a-4ad3-b5a3-306d4bbf51b5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputPriceVolatilityMember_be7adceb-37bc-4987-8c5c-2e0d9ce037e8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_MeasurementInputPriceVolatilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_b0abf042-6323-4536-8992-69c8ee906564" xlink:to="loc_us-gaap_MeasurementInputPriceVolatilityMember_be7adceb-37bc-4987-8c5c-2e0d9ce037e8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_b43e492b-a72f-4ba5-84c8-779539c81148" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_e4714b56-2132-4e84-9d47-01b9f5c95502" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_b43e492b-a72f-4ba5-84c8-779539c81148" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_b43e492b-a72f-4ba5-84c8-779539c81148_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_b43e492b-a72f-4ba5-84c8-779539c81148" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_b43e492b-a72f-4ba5-84c8-779539c81148_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_f5c42485-254f-4b9e-b1af-4073e7ce31ba" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_b43e492b-a72f-4ba5-84c8-779539c81148" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_f5c42485-254f-4b9e-b1af-4073e7ce31ba" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConvertibleDebtMember_e94c96ef-a6c5-4ede-85d3-799a1bc0d751" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ConvertibleDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_f5c42485-254f-4b9e-b1af-4073e7ce31ba" xlink:to="loc_us-gaap_ConvertibleDebtMember_e94c96ef-a6c5-4ede-85d3-799a1bc0d751" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://eosenergystorage.com/role/BorrowingsInterestExpenseDetails" xlink:type="simple" xlink:href="eose-20220930.xsd#BorrowingsInterestExpenseDetails"/>
  <link:definitionLink xlink:role="http://eosenergystorage.com/role/BorrowingsInterestExpenseDetails" xlink:type="extended" id="i476c25b76f79418785af23f98ad65d59_BorrowingsInterestExpenseDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_24eaa0c3-8faf-4d2f-a4ce-301f85a424f0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseDebtExcludingAmortization_4f9521e6-ad2a-458e-b7ea-1cd7065aa880" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InterestExpenseDebtExcludingAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_24eaa0c3-8faf-4d2f-a4ce-301f85a424f0" xlink:to="loc_us-gaap_InterestExpenseDebtExcludingAmortization_4f9521e6-ad2a-458e-b7ea-1cd7065aa880" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfDebtDiscountPremium_5619d3b3-0ecd-42cd-bfbb-6f0a0ccc61c7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AmortizationOfDebtDiscountPremium"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_24eaa0c3-8faf-4d2f-a4ce-301f85a424f0" xlink:to="loc_us-gaap_AmortizationOfDebtDiscountPremium_5619d3b3-0ecd-42cd-bfbb-6f0a0ccc61c7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfFinancingCosts_dbc0bd90-80fe-459e-bba0-efd46f93f820" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AmortizationOfFinancingCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_24eaa0c3-8faf-4d2f-a4ce-301f85a424f0" xlink:to="loc_us-gaap_AmortizationOfFinancingCosts_dbc0bd90-80fe-459e-bba0-efd46f93f820" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseDebt_121de117-972f-4c39-93d5-72a4ceaa212c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InterestExpenseDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_24eaa0c3-8faf-4d2f-a4ce-301f85a424f0" xlink:to="loc_us-gaap_InterestExpenseDebt_121de117-972f-4c39-93d5-72a4ceaa212c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_b4c46c11-d54b-4ef5-8115-15dcb01f7f75" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_24eaa0c3-8faf-4d2f-a4ce-301f85a424f0" xlink:to="loc_us-gaap_DebtInstrumentTable_b4c46c11-d54b-4ef5-8115-15dcb01f7f75" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_6ab2c30f-c466-47e3-8ddf-c0412447e226" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_b4c46c11-d54b-4ef5-8115-15dcb01f7f75" xlink:to="loc_us-gaap_DebtInstrumentAxis_6ab2c30f-c466-47e3-8ddf-c0412447e226" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_6ab2c30f-c466-47e3-8ddf-c0412447e226_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_6ab2c30f-c466-47e3-8ddf-c0412447e226" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_6ab2c30f-c466-47e3-8ddf-c0412447e226_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_c089cc28-b139-42c0-aeb9-2ac50b3ea885" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_6ab2c30f-c466-47e3-8ddf-c0412447e226" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_c089cc28-b139-42c0-aeb9-2ac50b3ea885" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_A2021ConvertibleNotesMember_024a7b51-13a3-44b3-be78-723b5b9c576e" xlink:href="eose-20220930.xsd#eose_A2021ConvertibleNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_c089cc28-b139-42c0-aeb9-2ac50b3ea885" xlink:to="loc_eose_A2021ConvertibleNotesMember_024a7b51-13a3-44b3-be78-723b5b9c576e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_SeniorSecuredTermLoanAgreementMember_e63d5be9-c2cf-4571-849a-da686306e38a" xlink:href="eose-20220930.xsd#eose_SeniorSecuredTermLoanAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_c089cc28-b139-42c0-aeb9-2ac50b3ea885" xlink:to="loc_eose_SeniorSecuredTermLoanAgreementMember_e63d5be9-c2cf-4571-849a-da686306e38a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_285bbf9e-0981-45cf-b09e-0d40011d3e6d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_b4c46c11-d54b-4ef5-8115-15dcb01f7f75" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_285bbf9e-0981-45cf-b09e-0d40011d3e6d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_285bbf9e-0981-45cf-b09e-0d40011d3e6d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_285bbf9e-0981-45cf-b09e-0d40011d3e6d" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_285bbf9e-0981-45cf-b09e-0d40011d3e6d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_8fbba90a-d285-48e3-a99e-41d0763dd68c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_285bbf9e-0981-45cf-b09e-0d40011d3e6d" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_8fbba90a-d285-48e3-a99e-41d0763dd68c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConvertibleDebtMember_32fa4704-dd10-412d-90ce-71ec35d942ef" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ConvertibleDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_8fbba90a-d285-48e3-a99e-41d0763dd68c" xlink:to="loc_us-gaap_ConvertibleDebtMember_32fa4704-dd10-412d-90ce-71ec35d942ef" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebtMember_f3a8bdd0-b5e2-4b20-9131-3a238e5ea21a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_8fbba90a-d285-48e3-a99e-41d0763dd68c" xlink:to="loc_us-gaap_SecuredDebtMember_f3a8bdd0-b5e2-4b20-9131-3a238e5ea21a" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://eosenergystorage.com/role/BorrowingsNetCarryingValueDetails" xlink:type="simple" xlink:href="eose-20220930.xsd#BorrowingsNetCarryingValueDetails"/>
  <link:definitionLink xlink:role="http://eosenergystorage.com/role/BorrowingsNetCarryingValueDetails" xlink:type="extended" id="i271af28965ba4767a2dedb85c9ae0fb6_BorrowingsNetCarryingValueDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_65f13de3-f4ee-41ab-a45e-49d50a160b5b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_84893a66-1c3f-48c1-8ddc-f37631553c73" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_65f13de3-f4ee-41ab-a45e-49d50a160b5b" xlink:to="loc_us-gaap_DebtInstrumentCarryingAmount_84893a66-1c3f-48c1-8ddc-f37631553c73" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentUnamortizedDiscount_f897a801-69ad-422a-91b3-09904468e283" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentUnamortizedDiscount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_65f13de3-f4ee-41ab-a45e-49d50a160b5b" xlink:to="loc_us-gaap_DebtInstrumentUnamortizedDiscount_f897a801-69ad-422a-91b3-09904468e283" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnamortizedDebtIssuanceExpense_111b5813-0f84-43c3-a31e-f5f73914cbff" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_UnamortizedDebtIssuanceExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_65f13de3-f4ee-41ab-a45e-49d50a160b5b" xlink:to="loc_us-gaap_UnamortizedDebtIssuanceExpense_111b5813-0f84-43c3-a31e-f5f73914cbff" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmbeddedDerivativeFairValueOfEmbeddedDerivativeLiability_43794769-d358-4880-a7be-9013516d8d1b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EmbeddedDerivativeFairValueOfEmbeddedDerivativeLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_65f13de3-f4ee-41ab-a45e-49d50a160b5b" xlink:to="loc_us-gaap_EmbeddedDerivativeFairValueOfEmbeddedDerivativeLiability_43794769-d358-4880-a7be-9013516d8d1b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_2a3e88b4-1fa9-4f6e-93ee-91e1388d325f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_65f13de3-f4ee-41ab-a45e-49d50a160b5b" xlink:to="loc_us-gaap_LongTermDebt_2a3e88b4-1fa9-4f6e-93ee-91e1388d325f" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_250b551d-4d5c-4a36-8659-f90a20fa2090" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_65f13de3-f4ee-41ab-a45e-49d50a160b5b" xlink:to="loc_us-gaap_DebtInstrumentTable_250b551d-4d5c-4a36-8659-f90a20fa2090" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_fe2c33f7-1faf-45fc-9293-cec139fcf47d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_250b551d-4d5c-4a36-8659-f90a20fa2090" xlink:to="loc_us-gaap_DebtInstrumentAxis_fe2c33f7-1faf-45fc-9293-cec139fcf47d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_fe2c33f7-1faf-45fc-9293-cec139fcf47d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_fe2c33f7-1faf-45fc-9293-cec139fcf47d" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_fe2c33f7-1faf-45fc-9293-cec139fcf47d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_73c550bb-92b1-4d46-a1c1-03651deb7ee3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_fe2c33f7-1faf-45fc-9293-cec139fcf47d" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_73c550bb-92b1-4d46-a1c1-03651deb7ee3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_A2021ConvertibleNotesMember_900be502-56c7-4bcd-834c-504c12b1cf4a" xlink:href="eose-20220930.xsd#eose_A2021ConvertibleNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_73c550bb-92b1-4d46-a1c1-03651deb7ee3" xlink:to="loc_eose_A2021ConvertibleNotesMember_900be502-56c7-4bcd-834c-504c12b1cf4a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_SeniorSecuredTermLoanAgreementMember_d9125d49-64ce-4838-b595-7c9f2904ef6e" xlink:href="eose-20220930.xsd#eose_SeniorSecuredTermLoanAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_73c550bb-92b1-4d46-a1c1-03651deb7ee3" xlink:to="loc_eose_SeniorSecuredTermLoanAgreementMember_d9125d49-64ce-4838-b595-7c9f2904ef6e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_ca9015d9-dbaa-4c01-bb35-f369aa88f04a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_250b551d-4d5c-4a36-8659-f90a20fa2090" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_ca9015d9-dbaa-4c01-bb35-f369aa88f04a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_ca9015d9-dbaa-4c01-bb35-f369aa88f04a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_ca9015d9-dbaa-4c01-bb35-f369aa88f04a" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_ca9015d9-dbaa-4c01-bb35-f369aa88f04a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_e9e552b1-f18c-4e0d-a571-1e5749e79da2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_ca9015d9-dbaa-4c01-bb35-f369aa88f04a" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_e9e552b1-f18c-4e0d-a571-1e5749e79da2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConvertibleDebtMember_33eb0f67-179b-4a94-93f9-3a13a43fb71c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ConvertibleDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_e9e552b1-f18c-4e0d-a571-1e5749e79da2" xlink:to="loc_us-gaap_ConvertibleDebtMember_33eb0f67-179b-4a94-93f9-3a13a43fb71c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebtMember_bad326c1-120e-4d97-a3c9-6e3412dae4d1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_e9e552b1-f18c-4e0d-a571-1e5749e79da2" xlink:to="loc_us-gaap_SecuredDebtMember_bad326c1-120e-4d97-a3c9-6e3412dae4d1" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://eosenergystorage.com/role/BorrowingsNotePayableDetails" xlink:type="simple" xlink:href="eose-20220930.xsd#BorrowingsNotePayableDetails"/>
  <link:definitionLink xlink:role="http://eosenergystorage.com/role/BorrowingsNotePayableDetails" xlink:type="extended" id="i4aa6cff1134844b3b3f2d7d0445f5516_BorrowingsNotePayableDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_19cb0536-7550-452f-a570-9645b5a61fcf" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferred1_d2a819d2-2a9a-4480-b2a3-60b78d3f39fd" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessCombinationConsiderationTransferred1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_19cb0536-7550-452f-a570-9645b5a61fcf" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferred1_d2a819d2-2a9a-4480-b2a3-60b78d3f39fd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesGross_4c505787-9667-474e-931d-ac019ea98e39" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PaymentsToAcquireBusinessesGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_19cb0536-7550-452f-a570-9645b5a61fcf" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesGross_4c505787-9667-474e-931d-ac019ea98e39" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtCurrent_f959deeb-0d1c-44f0-8772-7360a878fd65" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongTermDebtCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_19cb0536-7550-452f-a570-9645b5a61fcf" xlink:to="loc_us-gaap_LongTermDebtCurrent_f959deeb-0d1c-44f0-8772-7360a878fd65" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtNoncurrent_7eff8372-1731-4726-8f35-e3853cdd1991" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongTermDebtNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_19cb0536-7550-452f-a570-9645b5a61fcf" xlink:to="loc_us-gaap_LongTermDebtNoncurrent_7eff8372-1731-4726-8f35-e3853cdd1991" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainsLossesOnExtinguishmentOfDebt_d1568965-77e4-4974-ae8e-8282145e21d6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_GainsLossesOnExtinguishmentOfDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_19cb0536-7550-452f-a570-9645b5a61fcf" xlink:to="loc_us-gaap_GainsLossesOnExtinguishmentOfDebt_d1568965-77e4-4974-ae8e-8282145e21d6" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_a6b09e8b-f850-401a-815e-57387e186c57" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_19cb0536-7550-452f-a570-9645b5a61fcf" xlink:to="loc_us-gaap_DebtInstrumentTable_a6b09e8b-f850-401a-815e-57387e186c57" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_f3f3f9c4-6a0b-413b-8abf-5c0281386193" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_a6b09e8b-f850-401a-815e-57387e186c57" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_f3f3f9c4-6a0b-413b-8abf-5c0281386193" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_f3f3f9c4-6a0b-413b-8abf-5c0281386193_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_f3f3f9c4-6a0b-413b-8abf-5c0281386193" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_f3f3f9c4-6a0b-413b-8abf-5c0281386193_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_7af1edd9-e344-4d0f-bcc8-6fd865fe1c1a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_f3f3f9c4-6a0b-413b-8abf-5c0281386193" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_7af1edd9-e344-4d0f-bcc8-6fd865fe1c1a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_HIPOWERLLCMember_cfd1eaac-a694-4905-b7d0-5980243eeca8" xlink:href="eose-20220930.xsd#eose_HIPOWERLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_7af1edd9-e344-4d0f-bcc8-6fd865fe1c1a" xlink:to="loc_eose_HIPOWERLLCMember_cfd1eaac-a694-4905-b7d0-5980243eeca8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_2fc93b7d-7623-4de8-b14f-49368a1bff76" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_a6b09e8b-f850-401a-815e-57387e186c57" xlink:to="loc_us-gaap_DebtInstrumentAxis_2fc93b7d-7623-4de8-b14f-49368a1bff76" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_2fc93b7d-7623-4de8-b14f-49368a1bff76_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_2fc93b7d-7623-4de8-b14f-49368a1bff76" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_2fc93b7d-7623-4de8-b14f-49368a1bff76_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_5a5506af-8d41-4f87-8cbf-17be68329872" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_2fc93b7d-7623-4de8-b14f-49368a1bff76" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_5a5506af-8d41-4f87-8cbf-17be68329872" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_HiPowerPurchaseAgreementMember_98e611a0-dce1-4630-a239-80e33bed54db" xlink:href="eose-20220930.xsd#eose_HiPowerPurchaseAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_5a5506af-8d41-4f87-8cbf-17be68329872" xlink:to="loc_eose_HiPowerPurchaseAgreementMember_98e611a0-dce1-4630-a239-80e33bed54db" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_65002cf7-e51a-4740-85d3-1fe48c2b5349" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_a6b09e8b-f850-401a-815e-57387e186c57" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_65002cf7-e51a-4740-85d3-1fe48c2b5349" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_65002cf7-e51a-4740-85d3-1fe48c2b5349_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_65002cf7-e51a-4740-85d3-1fe48c2b5349" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_65002cf7-e51a-4740-85d3-1fe48c2b5349_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_2b67fe35-a82a-4a6d-9cc5-8f2d38b69df9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_65002cf7-e51a-4740-85d3-1fe48c2b5349" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_2b67fe35-a82a-4a6d-9cc5-8f2d38b69df9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NotesPayableOtherPayablesMember_f310ac56-c912-4f94-b87b-13555dc9f113" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NotesPayableOtherPayablesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_2b67fe35-a82a-4a6d-9cc5-8f2d38b69df9" xlink:to="loc_us-gaap_NotesPayableOtherPayablesMember_f310ac56-c912-4f94-b87b-13555dc9f113" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://eosenergystorage.com/role/WarrantsLiabilityRelatedPartyDetails" xlink:type="simple" xlink:href="eose-20220930.xsd#WarrantsLiabilityRelatedPartyDetails"/>
  <link:definitionLink xlink:role="http://eosenergystorage.com/role/WarrantsLiabilityRelatedPartyDetails" xlink:type="extended" id="ide4c93fa437c420da6d5b842e5924baf_WarrantsLiabilityRelatedPartyDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightLineItems_6f0f3aa0-596e-454f-aa5f-98d3bd48692f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfWarrantOrRightLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightOutstanding_167ad162-8a3c-4d2e-a63f-91edcacbb690" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfWarrantOrRightOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightLineItems_6f0f3aa0-596e-454f-aa5f-98d3bd48692f" xlink:to="loc_us-gaap_ClassOfWarrantOrRightOutstanding_167ad162-8a3c-4d2e-a63f-91edcacbb690" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WarrantsAndRightsOutstanding_d668215d-28d0-4c35-b315-6c0918cddb93" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_WarrantsAndRightsOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightLineItems_6f0f3aa0-596e-454f-aa5f-98d3bd48692f" xlink:to="loc_us-gaap_WarrantsAndRightsOutstanding_d668215d-28d0-4c35-b315-6c0918cddb93" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAdjustmentOfWarrants_b1ece017-518f-4fc6-8961-bee61adcc7b7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueAdjustmentOfWarrants"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightLineItems_6f0f3aa0-596e-454f-aa5f-98d3bd48692f" xlink:to="loc_us-gaap_FairValueAdjustmentOfWarrants_b1ece017-518f-4fc6-8961-bee61adcc7b7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightTable_81b4e88f-3aa9-4b55-920f-080d42461b9b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfWarrantOrRightTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ClassOfWarrantOrRightLineItems_6f0f3aa0-596e-454f-aa5f-98d3bd48692f" xlink:to="loc_us-gaap_ClassOfWarrantOrRightTable_81b4e88f-3aa9-4b55-920f-080d42461b9b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightAxis_205ecfcc-c44a-485d-8009-01bbc0b792fb" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfWarrantOrRightAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ClassOfWarrantOrRightTable_81b4e88f-3aa9-4b55-920f-080d42461b9b" xlink:to="loc_us-gaap_ClassOfWarrantOrRightAxis_205ecfcc-c44a-485d-8009-01bbc0b792fb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightDomain_205ecfcc-c44a-485d-8009-01bbc0b792fb_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfWarrantOrRightDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ClassOfWarrantOrRightAxis_205ecfcc-c44a-485d-8009-01bbc0b792fb" xlink:to="loc_us-gaap_ClassOfWarrantOrRightDomain_205ecfcc-c44a-485d-8009-01bbc0b792fb_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightDomain_2f40a3fa-746b-45dd-ae55-49308de6f1c6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfWarrantOrRightDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ClassOfWarrantOrRightAxis_205ecfcc-c44a-485d-8009-01bbc0b792fb" xlink:to="loc_us-gaap_ClassOfWarrantOrRightDomain_2f40a3fa-746b-45dd-ae55-49308de6f1c6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrivatePlacementMember_8e2e2617-49a0-4592-91e7-46103fea642e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PrivatePlacementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightDomain_2f40a3fa-746b-45dd-ae55-49308de6f1c6" xlink:to="loc_us-gaap_PrivatePlacementMember_8e2e2617-49a0-4592-91e7-46103fea642e" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://eosenergystorage.com/role/FairValueMeasurementFairValueofLiabilitiesDetails" xlink:type="simple" xlink:href="eose-20220930.xsd#FairValueMeasurementFairValueofLiabilitiesDetails"/>
  <link:definitionLink xlink:role="http://eosenergystorage.com/role/FairValueMeasurementFairValueofLiabilitiesDetails" xlink:type="extended" id="i2d4c250005124c7091ed2f3310b2d927_FairValueMeasurementFairValueofLiabilitiesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_dbadf3fc-ed51-4399-b800-87ae7e6aa3a1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WarrantsAndRightsOutstanding_08bbcc42-d0f5-46bc-a67b-df5f2623191a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_WarrantsAndRightsOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_dbadf3fc-ed51-4399-b800-87ae7e6aa3a1" xlink:to="loc_us-gaap_WarrantsAndRightsOutstanding_08bbcc42-d0f5-46bc-a67b-df5f2623191a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilities_f5738aab-ddf8-4f7f-83d1-50f973c2ab47" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_dbadf3fc-ed51-4399-b800-87ae7e6aa3a1" xlink:to="loc_us-gaap_DerivativeLiabilities_f5738aab-ddf8-4f7f-83d1-50f973c2ab47" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_b83fc6d2-81dc-4467-9456-a5b78a2685aa" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_dbadf3fc-ed51-4399-b800-87ae7e6aa3a1" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_b83fc6d2-81dc-4467-9456-a5b78a2685aa" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_9d6f2cd6-9b18-4e77-bbf5-15c743fe15c0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_b83fc6d2-81dc-4467-9456-a5b78a2685aa" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_9d6f2cd6-9b18-4e77-bbf5-15c743fe15c0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_9d6f2cd6-9b18-4e77-bbf5-15c743fe15c0_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_9d6f2cd6-9b18-4e77-bbf5-15c743fe15c0" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_9d6f2cd6-9b18-4e77-bbf5-15c743fe15c0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_b3ba80b9-dd90-45dd-9d9c-7f72536e4360" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_9d6f2cd6-9b18-4e77-bbf5-15c743fe15c0" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_b3ba80b9-dd90-45dd-9d9c-7f72536e4360" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_65c98674-2b75-4014-aa57-386fb32443ec" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_b3ba80b9-dd90-45dd-9d9c-7f72536e4360" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_65c98674-2b75-4014-aa57-386fb32443ec" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_163d1e8f-b9a3-468c-970e-4348f253457f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_b3ba80b9-dd90-45dd-9d9c-7f72536e4360" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_163d1e8f-b9a3-468c-970e-4348f253457f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_868f0cdc-305e-4997-910b-6039cca44956" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_b3ba80b9-dd90-45dd-9d9c-7f72536e4360" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_868f0cdc-305e-4997-910b-6039cca44956" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByLiabilityClassAxis_b2ca5bd8-4901-442c-b376-79715ae1abc9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueByLiabilityClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_b83fc6d2-81dc-4467-9456-a5b78a2685aa" xlink:to="loc_us-gaap_FairValueByLiabilityClassAxis_b2ca5bd8-4901-442c-b376-79715ae1abc9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_b2ca5bd8-4901-442c-b376-79715ae1abc9_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByLiabilityClassAxis_b2ca5bd8-4901-442c-b376-79715ae1abc9" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_b2ca5bd8-4901-442c-b376-79715ae1abc9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_d0ed28c9-9c5f-4135-a943-1218d1b25cab" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByLiabilityClassAxis_b2ca5bd8-4901-442c-b376-79715ae1abc9" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_d0ed28c9-9c5f-4135-a943-1218d1b25cab" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmbeddedDerivativeFinancialInstrumentsMember_2d1627c5-3e0a-4393-848f-da92f6fea01b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EmbeddedDerivativeFinancialInstrumentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_d0ed28c9-9c5f-4135-a943-1218d1b25cab" xlink:to="loc_us-gaap_EmbeddedDerivativeFinancialInstrumentsMember_2d1627c5-3e0a-4393-848f-da92f6fea01b" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://eosenergystorage.com/role/FairValueMeasurementCarryingValueandFairValueDetails" xlink:type="simple" xlink:href="eose-20220930.xsd#FairValueMeasurementCarryingValueandFairValueDetails"/>
  <link:definitionLink xlink:role="http://eosenergystorage.com/role/FairValueMeasurementCarryingValueandFairValueDetails" xlink:type="extended" id="i2f70179b73c743dc8a6201edb7f1e811_FairValueMeasurementCarryingValueandFairValueDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_c3eac414-4212-4c6c-9d8b-82968e9ec9d6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_7c700348-9b2b-4094-aadd-16dbc91f6350" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_c3eac414-4212-4c6c-9d8b-82968e9ec9d6" xlink:to="loc_us-gaap_LongTermDebt_7c700348-9b2b-4094-aadd-16dbc91f6350" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFairValue_c66e707a-5c85-428e-a156-99d276aa75ea" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_c3eac414-4212-4c6c-9d8b-82968e9ec9d6" xlink:to="loc_us-gaap_DebtInstrumentFairValue_c66e707a-5c85-428e-a156-99d276aa75ea" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNotesPayable_a5fbed48-63a3-44f0-a235-8e7e4ca23f6d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherNotesPayable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_c3eac414-4212-4c6c-9d8b-82968e9ec9d6" xlink:to="loc_us-gaap_OtherNotesPayable_a5fbed48-63a3-44f0-a235-8e7e4ca23f6d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_OtherNotesPayableFairValueDisclosure_9c7574ed-5463-49d4-8a85-cb831a07b293" xlink:href="eose-20220930.xsd#eose_OtherNotesPayableFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_c3eac414-4212-4c6c-9d8b-82968e9ec9d6" xlink:to="loc_eose_OtherNotesPayableFairValueDisclosure_9c7574ed-5463-49d4-8a85-cb831a07b293" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_NotesPayableRelatedPartiesFairValueDisclosure_31c4bd72-5513-4548-967a-f04c457f8207" xlink:href="eose-20220930.xsd#eose_NotesPayableRelatedPartiesFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_c3eac414-4212-4c6c-9d8b-82968e9ec9d6" xlink:to="loc_eose_NotesPayableRelatedPartiesFairValueDisclosure_31c4bd72-5513-4548-967a-f04c457f8207" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NotesPayableRelatedPartiesCurrentAndNoncurrent_0443b057-8638-4035-a430-611e767d7113" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NotesPayableRelatedPartiesCurrentAndNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_c3eac414-4212-4c6c-9d8b-82968e9ec9d6" xlink:to="loc_us-gaap_NotesPayableRelatedPartiesCurrentAndNoncurrent_0443b057-8638-4035-a430-611e767d7113" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_3054feb3-b33f-4d6c-868d-4043f61aadf1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_c3eac414-4212-4c6c-9d8b-82968e9ec9d6" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_3054feb3-b33f-4d6c-868d-4043f61aadf1" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_c9a954e6-2173-47a5-9edc-286bfb1a373f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_3054feb3-b33f-4d6c-868d-4043f61aadf1" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_c9a954e6-2173-47a5-9edc-286bfb1a373f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_c9a954e6-2173-47a5-9edc-286bfb1a373f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_c9a954e6-2173-47a5-9edc-286bfb1a373f" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_c9a954e6-2173-47a5-9edc-286bfb1a373f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_4471e6a5-4453-449e-8c45-b6464f448776" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_c9a954e6-2173-47a5-9edc-286bfb1a373f" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_4471e6a5-4453-449e-8c45-b6464f448776" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_77d91030-c4ab-4a85-8acf-db298ae307b7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_4471e6a5-4453-449e-8c45-b6464f448776" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_77d91030-c4ab-4a85-8acf-db298ae307b7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_5d8715fd-c67b-49ce-845c-c896d82e574e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_3054feb3-b33f-4d6c-868d-4043f61aadf1" xlink:to="loc_us-gaap_DebtInstrumentAxis_5d8715fd-c67b-49ce-845c-c896d82e574e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_5d8715fd-c67b-49ce-845c-c896d82e574e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_5d8715fd-c67b-49ce-845c-c896d82e574e" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_5d8715fd-c67b-49ce-845c-c896d82e574e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_9246c254-e2b7-430d-b031-fd11eb51b4f0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_5d8715fd-c67b-49ce-845c-c896d82e574e" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_9246c254-e2b7-430d-b031-fd11eb51b4f0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NotesReceivableMember_c0de4e25-b99d-4980-92a8-54b79ae5ca7d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NotesReceivableMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_9246c254-e2b7-430d-b031-fd11eb51b4f0" xlink:to="loc_us-gaap_NotesReceivableMember_c0de4e25-b99d-4980-92a8-54b79ae5ca7d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_A2021ConvertibleNotesMember_07b5da76-b6d0-49c8-99df-082baca80f85" xlink:href="eose-20220930.xsd#eose_A2021ConvertibleNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_9246c254-e2b7-430d-b031-fd11eb51b4f0" xlink:to="loc_eose_A2021ConvertibleNotesMember_07b5da76-b6d0-49c8-99df-082baca80f85" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_SeniorSecuredTermLoanAgreementMember_49d39931-f786-402f-81f1-fedaa47f99a1" xlink:href="eose-20220930.xsd#eose_SeniorSecuredTermLoanAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_9246c254-e2b7-430d-b031-fd11eb51b4f0" xlink:to="loc_eose_SeniorSecuredTermLoanAgreementMember_49d39931-f786-402f-81f1-fedaa47f99a1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_EquipmentFinancingFacilityMember_5001ff7d-50de-49c2-ba7e-a0dd31ce0a32" xlink:href="eose-20220930.xsd#eose_EquipmentFinancingFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_9246c254-e2b7-430d-b031-fd11eb51b4f0" xlink:to="loc_eose_EquipmentFinancingFacilityMember_5001ff7d-50de-49c2-ba7e-a0dd31ce0a32" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://eosenergystorage.com/role/CommitmentsandContingenciesDetails" xlink:type="simple" xlink:href="eose-20220930.xsd#CommitmentsandContingenciesDetails"/>
  <link:definitionLink xlink:role="http://eosenergystorage.com/role/CommitmentsandContingenciesDetails" xlink:type="extended" id="i1b978cd8f68e458bb04c7fd2f409e1fe_CommitmentsandContingenciesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCommitmentsLineItems_91dbd8e7-1acf-46ff-8431-10859ef6821e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherCommitmentsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceSheetAmount_f10f5fea-6b6f-49a9-9aac-0dbb16e908f8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceSheetAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherCommitmentsLineItems_91dbd8e7-1acf-46ff-8431-10859ef6821e" xlink:to="loc_us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceSheetAmount_f10f5fea-6b6f-49a9-9aac-0dbb16e908f8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LitigationSettlementAmountAwardedToOtherParty_db09a164-d16f-4ff1-a247-b721c528a09b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LitigationSettlementAmountAwardedToOtherParty"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherCommitmentsLineItems_91dbd8e7-1acf-46ff-8431-10859ef6821e" xlink:to="loc_us-gaap_LitigationSettlementAmountAwardedToOtherParty_db09a164-d16f-4ff1-a247-b721c528a09b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCommitmentsTable_62e32aac-0a28-4208-8536-34ce10d168a9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherCommitmentsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_OtherCommitmentsLineItems_91dbd8e7-1acf-46ff-8431-10859ef6821e" xlink:to="loc_us-gaap_OtherCommitmentsTable_62e32aac-0a28-4208-8536-34ce10d168a9" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrecordedUnconditionalPurchaseObligationByCategoryOfItemPurchasedAxis_589bbb7d-c79b-42f6-834c-8857e620024d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_UnrecordedUnconditionalPurchaseObligationByCategoryOfItemPurchasedAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_OtherCommitmentsTable_62e32aac-0a28-4208-8536-34ce10d168a9" xlink:to="loc_us-gaap_UnrecordedUnconditionalPurchaseObligationByCategoryOfItemPurchasedAxis_589bbb7d-c79b-42f6-834c-8857e620024d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnconditionalPurchaseObligationCategoryOfGoodsOrServicesAcquiredDomain_589bbb7d-c79b-42f6-834c-8857e620024d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_UnconditionalPurchaseObligationCategoryOfGoodsOrServicesAcquiredDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_UnrecordedUnconditionalPurchaseObligationByCategoryOfItemPurchasedAxis_589bbb7d-c79b-42f6-834c-8857e620024d" xlink:to="loc_us-gaap_UnconditionalPurchaseObligationCategoryOfGoodsOrServicesAcquiredDomain_589bbb7d-c79b-42f6-834c-8857e620024d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnconditionalPurchaseObligationCategoryOfGoodsOrServicesAcquiredDomain_ba263a88-048c-40cc-8cf2-97707f35a6e3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_UnconditionalPurchaseObligationCategoryOfGoodsOrServicesAcquiredDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_UnrecordedUnconditionalPurchaseObligationByCategoryOfItemPurchasedAxis_589bbb7d-c79b-42f6-834c-8857e620024d" xlink:to="loc_us-gaap_UnconditionalPurchaseObligationCategoryOfGoodsOrServicesAcquiredDomain_ba263a88-048c-40cc-8cf2-97707f35a6e3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_FirmCommitmentMember_0e65c372-45a0-4456-9066-9df676b50751" xlink:href="eose-20220930.xsd#eose_FirmCommitmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnconditionalPurchaseObligationCategoryOfGoodsOrServicesAcquiredDomain_ba263a88-048c-40cc-8cf2-97707f35a6e3" xlink:to="loc_eose_FirmCommitmentMember_0e65c372-45a0-4456-9066-9df676b50751" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_MinimumVolumeCommitmentMember_fe56fcb6-3a4e-409a-ac55-12a954ded28b" xlink:href="eose-20220930.xsd#eose_MinimumVolumeCommitmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnconditionalPurchaseObligationCategoryOfGoodsOrServicesAcquiredDomain_ba263a88-048c-40cc-8cf2-97707f35a6e3" xlink:to="loc_eose_MinimumVolumeCommitmentMember_fe56fcb6-3a4e-409a-ac55-12a954ded28b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CounterpartyNameAxis_1e2bb431-8fbb-48c1-927d-92a8f4b6dc9a" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_CounterpartyNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_OtherCommitmentsTable_62e32aac-0a28-4208-8536-34ce10d168a9" xlink:to="loc_srt_CounterpartyNameAxis_1e2bb431-8fbb-48c1-927d-92a8f4b6dc9a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_1e2bb431-8fbb-48c1-927d-92a8f4b6dc9a_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_1e2bb431-8fbb-48c1-927d-92a8f4b6dc9a" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_1e2bb431-8fbb-48c1-927d-92a8f4b6dc9a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_0b432fc3-68f8-4f44-9526-ac289729b04c" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_1e2bb431-8fbb-48c1-927d-92a8f4b6dc9a" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_0b432fc3-68f8-4f44-9526-ac289729b04c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_USDepartmentOfJusticeMember_3de7db8c-7551-4556-b7d9-2263c3a52519" xlink:href="eose-20220930.xsd#eose_USDepartmentOfJusticeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_0b432fc3-68f8-4f44-9526-ac289729b04c" xlink:to="loc_eose_USDepartmentOfJusticeMember_3de7db8c-7551-4556-b7d9-2263c3a52519" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_RelatorMember_5d6f8ca0-8fae-4089-92e8-597ab1f8a93d" xlink:href="eose-20220930.xsd#eose_RelatorMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_0b432fc3-68f8-4f44-9526-ac289729b04c" xlink:to="loc_eose_RelatorMember_5d6f8ca0-8fae-4089-92e8-597ab1f8a93d" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://eosenergystorage.com/role/StockBasedCompensationCompensationExpenseDetails" xlink:type="simple" xlink:href="eose-20220930.xsd#StockBasedCompensationCompensationExpenseDetails"/>
  <link:definitionLink xlink:role="http://eosenergystorage.com/role/StockBasedCompensationCompensationExpenseDetails" xlink:type="extended" id="ie10aa561e9b84598b165bef3502ad2aa_StockBasedCompensationCompensationExpenseDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_c76e37fe-8f36-4598-b405-6109394183fa" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_467b26a9-24eb-4407-b840-3e6544f60994" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AllocatedShareBasedCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_c76e37fe-8f36-4598-b405-6109394183fa" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_467b26a9-24eb-4407-b840-3e6544f60994" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_e52f2d54-5518-430d-9604-1fbcc3158ca8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_c76e37fe-8f36-4598-b405-6109394183fa" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_e52f2d54-5518-430d-9604-1fbcc3158ca8" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_d4c66edc-6108-4f63-9fd5-f9cb679b6048" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_e52f2d54-5518-430d-9604-1fbcc3158ca8" xlink:to="loc_us-gaap_AwardTypeAxis_d4c66edc-6108-4f63-9fd5-f9cb679b6048" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_d4c66edc-6108-4f63-9fd5-f9cb679b6048_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_d4c66edc-6108-4f63-9fd5-f9cb679b6048" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_d4c66edc-6108-4f63-9fd5-f9cb679b6048_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_a31e5a8e-213b-4596-b1c9-4a8bb583f029" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_d4c66edc-6108-4f63-9fd5-f9cb679b6048" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_a31e5a8e-213b-4596-b1c9-4a8bb583f029" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_a603d4c4-d1bf-46a3-a322-244d5aee8646" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EmployeeStockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_a31e5a8e-213b-4596-b1c9-4a8bb583f029" xlink:to="loc_us-gaap_EmployeeStockOptionMember_a603d4c4-d1bf-46a3-a322-244d5aee8646" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_6d75a06e-ac65-470d-a715-e11a83bbad0b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_a31e5a8e-213b-4596-b1c9-4a8bb583f029" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_6d75a06e-ac65-470d-a715-e11a83bbad0b" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://eosenergystorage.com/role/StockBasedCompensationSummaryofRestrictedUnitActivityDetails" xlink:type="simple" xlink:href="eose-20220930.xsd#StockBasedCompensationSummaryofRestrictedUnitActivityDetails"/>
  <link:definitionLink xlink:role="http://eosenergystorage.com/role/StockBasedCompensationSummaryofRestrictedUnitActivityDetails" xlink:type="extended" id="i89f23ca29ad3418196de1adcabe8aad1_StockBasedCompensationSummaryofRestrictedUnitActivityDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_25ac42cc-e944-4280-9023-7d4dcf2a73ca" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_18b45265-a75a-4afd-8992-3ed3e4e711ce" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_25ac42cc-e944-4280-9023-7d4dcf2a73ca" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_18b45265-a75a-4afd-8992-3ed3e4e711ce" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_04be5c44-906c-4ca6-97be-73612145af9e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_18b45265-a75a-4afd-8992-3ed3e4e711ce" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_04be5c44-906c-4ca6-97be-73612145af9e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_a542be60-3025-4448-8ffb-89f6d543626b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_18b45265-a75a-4afd-8992-3ed3e4e711ce" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_a542be60-3025-4448-8ffb-89f6d543626b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_cb25e97c-835d-49da-b591-4bfa82d8953b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_18b45265-a75a-4afd-8992-3ed3e4e711ce" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_cb25e97c-835d-49da-b591-4bfa82d8953b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_88a4ce07-b4d7-4f82-a6bb-a275ca0f72ad" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_18b45265-a75a-4afd-8992-3ed3e4e711ce" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_88a4ce07-b4d7-4f82-a6bb-a275ca0f72ad" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_68c7aa25-c58e-4095-849b-18a221a02b14" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_b5519653-5b85-4b68-9e2b-a0ecee008c89" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_25ac42cc-e944-4280-9023-7d4dcf2a73ca" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_b5519653-5b85-4b68-9e2b-a0ecee008c89" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_430d558a-d92f-46e9-a9df-20bd05750da7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_b5519653-5b85-4b68-9e2b-a0ecee008c89" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_430d558a-d92f-46e9-a9df-20bd05750da7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_c43d77af-13b1-4ba6-8471-ac5fa3e7cc03" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_b5519653-5b85-4b68-9e2b-a0ecee008c89" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_c43d77af-13b1-4ba6-8471-ac5fa3e7cc03" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_303ff231-2a73-46c1-bf7b-99bdf526fa72" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_b5519653-5b85-4b68-9e2b-a0ecee008c89" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_303ff231-2a73-46c1-bf7b-99bdf526fa72" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_ed31d65a-6656-4893-b5cf-c9eec21658fc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_b5519653-5b85-4b68-9e2b-a0ecee008c89" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_ed31d65a-6656-4893-b5cf-c9eec21658fc" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_1e96ca45-48a4-46eb-a658-5f242755be1c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_ad11c788-1821-44d9-9573-ab4e576ccd6e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_25ac42cc-e944-4280-9023-7d4dcf2a73ca" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_ad11c788-1821-44d9-9573-ab4e576ccd6e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_5582821d-ea78-4f44-b7e2-5953dbedcbf1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_ad11c788-1821-44d9-9573-ab4e576ccd6e" xlink:to="loc_us-gaap_AwardTypeAxis_5582821d-ea78-4f44-b7e2-5953dbedcbf1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_5582821d-ea78-4f44-b7e2-5953dbedcbf1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_5582821d-ea78-4f44-b7e2-5953dbedcbf1" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_5582821d-ea78-4f44-b7e2-5953dbedcbf1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_9147a355-d091-4e06-8a27-824877450fd6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_5582821d-ea78-4f44-b7e2-5953dbedcbf1" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_9147a355-d091-4e06-8a27-824877450fd6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_2fa7d308-b3c6-455a-a406-4cf6b099ea82" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_9147a355-d091-4e06-8a27-824877450fd6" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_2fa7d308-b3c6-455a-a406-4cf6b099ea82" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://eosenergystorage.com/role/StockBasedCompensationNarrativesDetails" xlink:type="simple" xlink:href="eose-20220930.xsd#StockBasedCompensationNarrativesDetails"/>
  <link:definitionLink xlink:role="http://eosenergystorage.com/role/StockBasedCompensationNarrativesDetails" xlink:type="extended" id="iee20c76c51e2434abf0189e25b92fcdc_StockBasedCompensationNarrativesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_5365167b-e70f-417e-a4f0-7bbdf072e8fd" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized_36d134a0-646b-4886-b05e-e156665b5097" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_5365167b-e70f-417e-a4f0-7bbdf072e8fd" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized_36d134a0-646b-4886-b05e-e156665b5097" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockCapitalSharesReservedForFutureIssuance_650cf6bb-0597-4e41-9b0b-748038adc7e6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockCapitalSharesReservedForFutureIssuance"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_5365167b-e70f-417e-a4f0-7bbdf072e8fd" xlink:to="loc_us-gaap_CommonStockCapitalSharesReservedForFutureIssuance_650cf6bb-0597-4e41-9b0b-748038adc7e6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod_3ff9803a-0de0-4c8f-a403-8249525180f7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_5365167b-e70f-417e-a4f0-7bbdf072e8fd" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod_3ff9803a-0de0-4c8f-a403-8249525180f7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_92be8450-a2b4-4f24-ab00-1b1f01c68ef7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_5365167b-e70f-417e-a4f0-7bbdf072e8fd" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_92be8450-a2b4-4f24-ab00-1b1f01c68ef7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_39979055-0948-466c-8370-505eac2b8c05" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_5365167b-e70f-417e-a4f0-7bbdf072e8fd" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_39979055-0948-466c-8370-505eac2b8c05" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod_c82960a4-8123-42cd-8a7c-3d93e445cb56" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_5365167b-e70f-417e-a4f0-7bbdf072e8fd" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod_c82960a4-8123-42cd-8a7c-3d93e445cb56" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber_09b0d47d-083e-40f2-9f92-e7900c4313c4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_5365167b-e70f-417e-a4f0-7bbdf072e8fd" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber_09b0d47d-083e-40f2-9f92-e7900c4313c4" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber_b51e4b86-4bc3-43cb-aacb-be00a6b33847" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_5365167b-e70f-417e-a4f0-7bbdf072e8fd" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber_b51e4b86-4bc3-43cb-aacb-be00a6b33847" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_0e1f5a97-a2f4-4eac-beae-ae8d9ada8fcc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_5365167b-e70f-417e-a4f0-7bbdf072e8fd" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_0e1f5a97-a2f4-4eac-beae-ae8d9ada8fcc" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions_8ea0b19f-90a8-4f66-b328-0268fece44b2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_5365167b-e70f-417e-a4f0-7bbdf072e8fd" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions_8ea0b19f-90a8-4f66-b328-0268fece44b2" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions_771b5c3f-02a3-48ff-8e79-8c997932b1e6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_5365167b-e70f-417e-a4f0-7bbdf072e8fd" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions_771b5c3f-02a3-48ff-8e79-8c997932b1e6" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_029ba892-3f32-4422-9d5f-77a876c58616" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_5365167b-e70f-417e-a4f0-7bbdf072e8fd" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_029ba892-3f32-4422-9d5f-77a876c58616" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_381a3f1e-a04b-40d1-967b-a2bb026d5a27" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_5365167b-e70f-417e-a4f0-7bbdf072e8fd" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_381a3f1e-a04b-40d1-967b-a2bb026d5a27" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_e7e9c492-d276-4509-baa3-0356e1cb2663" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_381a3f1e-a04b-40d1-967b-a2bb026d5a27" xlink:to="loc_us-gaap_AwardTypeAxis_e7e9c492-d276-4509-baa3-0356e1cb2663" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_e7e9c492-d276-4509-baa3-0356e1cb2663_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_e7e9c492-d276-4509-baa3-0356e1cb2663" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_e7e9c492-d276-4509-baa3-0356e1cb2663_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_8c3186ce-12c4-458b-8ca7-f3eaced80941" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_e7e9c492-d276-4509-baa3-0356e1cb2663" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_8c3186ce-12c4-458b-8ca7-f3eaced80941" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_213d0a4e-7a8d-4291-bfa0-939a03b457fc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EmployeeStockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_8c3186ce-12c4-458b-8ca7-f3eaced80941" xlink:to="loc_us-gaap_EmployeeStockOptionMember_213d0a4e-7a8d-4291-bfa0-939a03b457fc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_eb4c4036-3316-496b-ab27-8dc8e7542a5c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_8c3186ce-12c4-458b-8ca7-f3eaced80941" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_eb4c4036-3316-496b-ab27-8dc8e7542a5c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_90de962e-93d3-4acd-917b-32640f499c0c" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_381a3f1e-a04b-40d1-967b-a2bb026d5a27" xlink:to="loc_srt_RangeAxis_90de962e-93d3-4acd-917b-32640f499c0c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_90de962e-93d3-4acd-917b-32640f499c0c_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_90de962e-93d3-4acd-917b-32640f499c0c" xlink:to="loc_srt_RangeMember_90de962e-93d3-4acd-917b-32640f499c0c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_3201cf86-9b8f-4d41-b241-a2dfce4c9953" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_90de962e-93d3-4acd-917b-32640f499c0c" xlink:to="loc_srt_RangeMember_3201cf86-9b8f-4d41-b241-a2dfce4c9953" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_32e8ef1d-d3b7-4298-a6f4-7fdab4fc988a" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_3201cf86-9b8f-4d41-b241-a2dfce4c9953" xlink:to="loc_srt_MinimumMember_32e8ef1d-d3b7-4298-a6f4-7fdab4fc988a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_f5f2a4ec-a36d-4366-8edc-9e428607b57d" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_3201cf86-9b8f-4d41-b241-a2dfce4c9953" xlink:to="loc_srt_MaximumMember_f5f2a4ec-a36d-4366-8edc-9e428607b57d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_WeightedAverageMember_a9a3501b-dc83-4892-93c4-310b2c30a4ec" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_WeightedAverageMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_3201cf86-9b8f-4d41-b241-a2dfce4c9953" xlink:to="loc_srt_WeightedAverageMember_a9a3501b-dc83-4892-93c4-310b2c30a4ec" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VestingAxis_5687c955-36e8-46b3-a7d4-879e44a42c47" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_VestingAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_381a3f1e-a04b-40d1-967b-a2bb026d5a27" xlink:to="loc_us-gaap_VestingAxis_5687c955-36e8-46b3-a7d4-879e44a42c47" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VestingDomain_5687c955-36e8-46b3-a7d4-879e44a42c47_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_VestingDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VestingAxis_5687c955-36e8-46b3-a7d4-879e44a42c47" xlink:to="loc_us-gaap_VestingDomain_5687c955-36e8-46b3-a7d4-879e44a42c47_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VestingDomain_183daeef-9ef8-4240-b74c-28548f366214" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_VestingDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VestingAxis_5687c955-36e8-46b3-a7d4-879e44a42c47" xlink:to="loc_us-gaap_VestingDomain_183daeef-9ef8-4240-b74c-28548f366214" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_PerformanceAndServiceConditionsMember_44b1638d-813d-4426-97a2-add5ef45f934" xlink:href="eose-20220930.xsd#eose_PerformanceAndServiceConditionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VestingDomain_183daeef-9ef8-4240-b74c-28548f366214" xlink:to="loc_eose_PerformanceAndServiceConditionsMember_44b1638d-813d-4426-97a2-add5ef45f934" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://eosenergystorage.com/role/ShareholdersDeficitEquityAdditionalInformationDetails" xlink:type="simple" xlink:href="eose-20220930.xsd#ShareholdersDeficitEquityAdditionalInformationDetails"/>
  <link:definitionLink xlink:role="http://eosenergystorage.com/role/ShareholdersDeficitEquityAdditionalInformationDetails" xlink:type="extended" id="i70b3cc07fb5942e7919a39411da3d5cf_ShareholdersDeficitEquityAdditionalInformationDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockLineItems_e80f5ae5-7298-461c-a734-f1f548b846b6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfStockLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockSharesAuthorized_a759d1a3-52d8-431c-af00-8e66bad02a62" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PreferredStockSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_e80f5ae5-7298-461c-a734-f1f548b846b6" xlink:to="loc_us-gaap_PreferredStockSharesAuthorized_a759d1a3-52d8-431c-af00-8e66bad02a62" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockSharesIssued_f2c683a1-6e74-4173-8d23-adec66d7275b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PreferredStockSharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_e80f5ae5-7298-461c-a734-f1f548b846b6" xlink:to="loc_us-gaap_PreferredStockSharesIssued_f2c683a1-6e74-4173-8d23-adec66d7275b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockSharesOutstanding_525e4fcd-1c0d-4b40-aad0-14fcdb3f695c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PreferredStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_e80f5ae5-7298-461c-a734-f1f548b846b6" xlink:to="loc_us-gaap_PreferredStockSharesOutstanding_525e4fcd-1c0d-4b40-aad0-14fcdb3f695c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockParOrStatedValuePerShare_919ed1f1-9246-4861-a48e-b106ceddb3d4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockParOrStatedValuePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_e80f5ae5-7298-461c-a734-f1f548b846b6" xlink:to="loc_us-gaap_CommonStockParOrStatedValuePerShare_919ed1f1-9246-4861-a48e-b106ceddb3d4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesAuthorized_883cbd4b-12e2-4653-8acc-dba4d3125fff" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_e80f5ae5-7298-461c-a734-f1f548b846b6" xlink:to="loc_us-gaap_CommonStockSharesAuthorized_883cbd4b-12e2-4653-8acc-dba4d3125fff" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_CommonStockVotingRightsNumberOfVotes_5f0ac591-520a-42f5-8e27-ce961c7ec4a3" xlink:href="eose-20220930.xsd#eose_CommonStockVotingRightsNumberOfVotes"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_e80f5ae5-7298-461c-a734-f1f548b846b6" xlink:to="loc_eose_CommonStockVotingRightsNumberOfVotes_5f0ac591-520a-42f5-8e27-ce961c7ec4a3" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesIssued_475e9097-9421-4ec5-a291-34e6cda0c1a4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockSharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_e80f5ae5-7298-461c-a734-f1f548b846b6" xlink:to="loc_us-gaap_CommonStockSharesIssued_475e9097-9421-4ec5-a291-34e6cda0c1a4" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_7c79a1bd-0ba5-41e2-99aa-ec3552bc8e99" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_e80f5ae5-7298-461c-a734-f1f548b846b6" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_7c79a1bd-0ba5-41e2-99aa-ec3552bc8e99" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_BusinessCombinationContingentConsiderationEquityEarnoutPeriod_871498bf-4946-41a0-a515-61fbbeb399a3" xlink:href="eose-20220930.xsd#eose_BusinessCombinationContingentConsiderationEquityEarnoutPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_e80f5ae5-7298-461c-a734-f1f548b846b6" xlink:to="loc_eose_BusinessCombinationContingentConsiderationEquityEarnoutPeriod_871498bf-4946-41a0-a515-61fbbeb399a3" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_BusinessCombinationContingentConsiderationEquityEarnoutPeriodThresholdBusinessDays_807d05a7-2a5b-4c33-890f-e25b15783db1" xlink:href="eose-20220930.xsd#eose_BusinessCombinationContingentConsiderationEquityEarnoutPeriodThresholdBusinessDays"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_e80f5ae5-7298-461c-a734-f1f548b846b6" xlink:to="loc_eose_BusinessCombinationContingentConsiderationEquityEarnoutPeriodThresholdBusinessDays_807d05a7-2a5b-4c33-890f-e25b15783db1" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_BusinessCombinationContingentConsiderationEquityEarnoutPeriodStockPriceTrigger_4a12b086-4869-4029-9cef-acb6464c895a" xlink:href="eose-20220930.xsd#eose_BusinessCombinationContingentConsiderationEquityEarnoutPeriodStockPriceTrigger"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_e80f5ae5-7298-461c-a734-f1f548b846b6" xlink:to="loc_eose_BusinessCombinationContingentConsiderationEquityEarnoutPeriodStockPriceTrigger_4a12b086-4869-4029-9cef-acb6464c895a" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_BusinessCombinationContingentConsiderationEquityEarnoutPeriodThresholdTradingDays_f2a9c3aa-7b24-4c98-b709-370038f74795" xlink:href="eose-20220930.xsd#eose_BusinessCombinationContingentConsiderationEquityEarnoutPeriodThresholdTradingDays"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_e80f5ae5-7298-461c-a734-f1f548b846b6" xlink:to="loc_eose_BusinessCombinationContingentConsiderationEquityEarnoutPeriodThresholdTradingDays_f2a9c3aa-7b24-4c98-b709-370038f74795" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_BusinessCombinationContingentConsiderationEquityEarnoutPeriodThresholdConsecutiveTradingDays_b1874258-a585-422c-9e8b-c1e6f1097b8c" xlink:href="eose-20220930.xsd#eose_BusinessCombinationContingentConsiderationEquityEarnoutPeriodThresholdConsecutiveTradingDays"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_e80f5ae5-7298-461c-a734-f1f548b846b6" xlink:to="loc_eose_BusinessCombinationContingentConsiderationEquityEarnoutPeriodThresholdConsecutiveTradingDays_b1874258-a585-422c-9e8b-c1e6f1097b8c" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_StockIssuedDuringPeriodSharesContingentlyIssuableStock_4667099f-a520-47ab-8e33-07c1bc34738c" xlink:href="eose-20220930.xsd#eose_StockIssuedDuringPeriodSharesContingentlyIssuableStock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_e80f5ae5-7298-461c-a734-f1f548b846b6" xlink:to="loc_eose_StockIssuedDuringPeriodSharesContingentlyIssuableStock_4667099f-a520-47ab-8e33-07c1bc34738c" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_DerivativeInstrumentContingentConsiderationLiabilityShares_de8618c7-272e-4438-be23-d651b6f5da52" xlink:href="eose-20220930.xsd#eose_DerivativeInstrumentContingentConsiderationLiabilityShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_e80f5ae5-7298-461c-a734-f1f548b846b6" xlink:to="loc_eose_DerivativeInstrumentContingentConsiderationLiabilityShares_de8618c7-272e-4438-be23-d651b6f5da52" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_DerivativeInstrumentContingentConsiderationLiabilityEarnoutPeriod_4196e6e7-7e3d-44e1-b600-36d1b51f75d9" xlink:href="eose-20220930.xsd#eose_DerivativeInstrumentContingentConsiderationLiabilityEarnoutPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_e80f5ae5-7298-461c-a734-f1f548b846b6" xlink:to="loc_eose_DerivativeInstrumentContingentConsiderationLiabilityEarnoutPeriod_4196e6e7-7e3d-44e1-b600-36d1b51f75d9" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_DerivativeInstrumentContingentConsiderationLiabilityEarnoutPeriodStockPriceTrigger_c3eec8d6-5fe5-4002-9cd1-320e060b90dc" xlink:href="eose-20220930.xsd#eose_DerivativeInstrumentContingentConsiderationLiabilityEarnoutPeriodStockPriceTrigger"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_e80f5ae5-7298-461c-a734-f1f548b846b6" xlink:to="loc_eose_DerivativeInstrumentContingentConsiderationLiabilityEarnoutPeriodStockPriceTrigger_c3eec8d6-5fe5-4002-9cd1-320e060b90dc" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_DerivativeInstrumentContingentConsiderationLiabilityEarnoutPeriodThresholdTradingDays_c2aa3dc8-6abb-4f2a-8eed-d2ef3d020b1f" xlink:href="eose-20220930.xsd#eose_DerivativeInstrumentContingentConsiderationLiabilityEarnoutPeriodThresholdTradingDays"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_e80f5ae5-7298-461c-a734-f1f548b846b6" xlink:to="loc_eose_DerivativeInstrumentContingentConsiderationLiabilityEarnoutPeriodThresholdTradingDays_c2aa3dc8-6abb-4f2a-8eed-d2ef3d020b1f" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_DerivativeInstrumentContingentConsiderationLiabilityEarnoutPeriodThresholdConsecutiveTradingDays_2b42758f-2213-49f0-adad-0ad3fe342697" xlink:href="eose-20220930.xsd#eose_DerivativeInstrumentContingentConsiderationLiabilityEarnoutPeriodThresholdConsecutiveTradingDays"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_e80f5ae5-7298-461c-a734-f1f548b846b6" xlink:to="loc_eose_DerivativeInstrumentContingentConsiderationLiabilityEarnoutPeriodThresholdConsecutiveTradingDays_2b42758f-2213-49f0-adad-0ad3fe342697" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation_d3050300-4d77-4848-8599-d8bc3a60a7e1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_e80f5ae5-7298-461c-a734-f1f548b846b6" xlink:to="loc_us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation_d3050300-4d77-4848-8599-d8bc3a60a7e1" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights_ecacb95c-da0d-4d3b-9d00-f98bcb24e5e2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_e80f5ae5-7298-461c-a734-f1f548b846b6" xlink:to="loc_us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights_ecacb95c-da0d-4d3b-9d00-f98bcb24e5e2" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1_1366fe91-8cad-4a18-b571-106eaf8fce83" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_e80f5ae5-7298-461c-a734-f1f548b846b6" xlink:to="loc_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1_1366fe91-8cad-4a18-b571-106eaf8fce83" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_StockIssuedDuringPeriodSharesWarrantsExercised_89e0ba9d-2a68-497a-9fbb-b2d8465f1a96" xlink:href="eose-20220930.xsd#eose_StockIssuedDuringPeriodSharesWarrantsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_e80f5ae5-7298-461c-a734-f1f548b846b6" xlink:to="loc_eose_StockIssuedDuringPeriodSharesWarrantsExercised_89e0ba9d-2a68-497a-9fbb-b2d8465f1a96" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightOutstanding_76fff6fa-8711-49ac-9fd7-f339e03ddcea" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfWarrantOrRightOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_e80f5ae5-7298-461c-a734-f1f548b846b6" xlink:to="loc_us-gaap_ClassOfWarrantOrRightOutstanding_76fff6fa-8711-49ac-9fd7-f339e03ddcea" xlink:type="arc" order="23"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_SaleOfStockAuthorizedAmountValue_c38916af-b641-4467-ba82-b75b9d8e326e" xlink:href="eose-20220930.xsd#eose_SaleOfStockAuthorizedAmountValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_e80f5ae5-7298-461c-a734-f1f548b846b6" xlink:to="loc_eose_SaleOfStockAuthorizedAmountValue_c38916af-b641-4467-ba82-b75b9d8e326e" xlink:type="arc" order="24"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockConsiderationReceivedPerTransaction_24e22d59-c1d4-4c67-bd16-ad6d2031539f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SaleOfStockConsiderationReceivedPerTransaction"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_e80f5ae5-7298-461c-a734-f1f548b846b6" xlink:to="loc_us-gaap_SaleOfStockConsiderationReceivedPerTransaction_24e22d59-c1d4-4c67-bd16-ad6d2031539f" xlink:type="arc" order="25"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_SharePriceAsPercentageOfMarketPrice_d66b8f60-5204-4d2b-9d33-c423b9f7d144" xlink:href="eose-20220930.xsd#eose_SharePriceAsPercentageOfMarketPrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_e80f5ae5-7298-461c-a734-f1f548b846b6" xlink:to="loc_eose_SharePriceAsPercentageOfMarketPrice_d66b8f60-5204-4d2b-9d33-c423b9f7d144" xlink:type="arc" order="26"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockPercentageOfOwnershipAfterTransaction_905f689a-d592-4c6b-8335-82780db022b5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SaleOfStockPercentageOfOwnershipAfterTransaction"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_e80f5ae5-7298-461c-a734-f1f548b846b6" xlink:to="loc_us-gaap_SaleOfStockPercentageOfOwnershipAfterTransaction_905f689a-d592-4c6b-8335-82780db022b5" xlink:type="arc" order="27"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_SaleOfStockOwnershipThresholdAfterExchangeCapPercent_8100c343-288c-45bb-8817-f72dd2f71d23" xlink:href="eose-20220930.xsd#eose_SaleOfStockOwnershipThresholdAfterExchangeCapPercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_e80f5ae5-7298-461c-a734-f1f548b846b6" xlink:to="loc_eose_SaleOfStockOwnershipThresholdAfterExchangeCapPercent_8100c343-288c-45bb-8817-f72dd2f71d23" xlink:type="arc" order="28"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_StockIssuedDuringPeriodSharesCommitmentFee_36e3d36f-983e-4137-9e14-56c244d9366b" xlink:href="eose-20220930.xsd#eose_StockIssuedDuringPeriodSharesCommitmentFee"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_e80f5ae5-7298-461c-a734-f1f548b846b6" xlink:to="loc_eose_StockIssuedDuringPeriodSharesCommitmentFee_36e3d36f-983e-4137-9e14-56c244d9366b" xlink:type="arc" order="29"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_SaleOfStockCommitmentFee_c1d3b738-70eb-474d-b2f1-eb1b95c116ac" xlink:href="eose-20220930.xsd#eose_SaleOfStockCommitmentFee"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_e80f5ae5-7298-461c-a734-f1f548b846b6" xlink:to="loc_eose_SaleOfStockCommitmentFee_c1d3b738-70eb-474d-b2f1-eb1b95c116ac" xlink:type="arc" order="30"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockConsiderationReceivedOnTransaction_f9d4647e-40ad-4aca-bf64-02db9caea031" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SaleOfStockConsiderationReceivedOnTransaction"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_e80f5ae5-7298-461c-a734-f1f548b846b6" xlink:to="loc_us-gaap_SaleOfStockConsiderationReceivedOnTransaction_f9d4647e-40ad-4aca-bf64-02db9caea031" xlink:type="arc" order="31"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction_6f499224-156d-4107-9269-a66c38a59c35" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_e80f5ae5-7298-461c-a734-f1f548b846b6" xlink:to="loc_us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction_6f499224-156d-4107-9269-a66c38a59c35" xlink:type="arc" order="32"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockPricePerShare_a5595f14-537d-4327-b737-56a14b1405ad" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SaleOfStockPricePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_e80f5ae5-7298-461c-a734-f1f548b846b6" xlink:to="loc_us-gaap_SaleOfStockPricePerShare_a5595f14-537d-4327-b737-56a14b1405ad" xlink:type="arc" order="33"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtConversionConvertedInstrumentSharesIssued1_66d95ace-0d19-42df-87f2-45a748b2831f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtConversionConvertedInstrumentSharesIssued1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_e80f5ae5-7298-461c-a734-f1f548b846b6" xlink:to="loc_us-gaap_DebtConversionConvertedInstrumentSharesIssued1_66d95ace-0d19-42df-87f2-45a748b2831f" xlink:type="arc" order="34"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentConvertibleConversionPrice1_b806c892-e7cb-47fb-b0b5-f7bbeaa3d56b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentConvertibleConversionPrice1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_e80f5ae5-7298-461c-a734-f1f548b846b6" xlink:to="loc_us-gaap_DebtInstrumentConvertibleConversionPrice1_b806c892-e7cb-47fb-b0b5-f7bbeaa3d56b" xlink:type="arc" order="35"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtConversionConvertedInstrumentAmount1_118533c1-06f3-4de2-9255-8cbc55b33921" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtConversionConvertedInstrumentAmount1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_e80f5ae5-7298-461c-a734-f1f548b846b6" xlink:to="loc_us-gaap_DebtConversionConvertedInstrumentAmount1_118533c1-06f3-4de2-9255-8cbc55b33921" xlink:type="arc" order="36"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_SaleOfStockPercentageOfCommissionOnGrossProceeds_8edccd9b-d9ff-4585-a316-a6eff5984aeb" xlink:href="eose-20220930.xsd#eose_SaleOfStockPercentageOfCommissionOnGrossProceeds"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_e80f5ae5-7298-461c-a734-f1f548b846b6" xlink:to="loc_eose_SaleOfStockPercentageOfCommissionOnGrossProceeds_8edccd9b-d9ff-4585-a316-a6eff5984aeb" xlink:type="arc" order="37"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfStockByClassTable_0876cdce-94b2-468f-8400-bd43ecc8fc1d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfStockByClassTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ClassOfStockLineItems_e80f5ae5-7298-461c-a734-f1f548b846b6" xlink:to="loc_us-gaap_ScheduleOfStockByClassTable_0876cdce-94b2-468f-8400-bd43ecc8fc1d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsidiarySaleOfStockAxis_54348ab7-3f31-4a8d-bc65-0803a288939d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SubsidiarySaleOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_0876cdce-94b2-468f-8400-bd43ecc8fc1d" xlink:to="loc_us-gaap_SubsidiarySaleOfStockAxis_54348ab7-3f31-4a8d-bc65-0803a288939d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_54348ab7-3f31-4a8d-bc65-0803a288939d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SaleOfStockNameOfTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_54348ab7-3f31-4a8d-bc65-0803a288939d" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_54348ab7-3f31-4a8d-bc65-0803a288939d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_f8d05952-ef7f-4a2d-b51f-ad61947760ee" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SaleOfStockNameOfTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_54348ab7-3f31-4a8d-bc65-0803a288939d" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_f8d05952-ef7f-4a2d-b51f-ad61947760ee" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_AtTheMarketProgramMember_9f868766-6ac1-4846-bd65-545d2fd82a71" xlink:href="eose-20220930.xsd#eose_AtTheMarketProgramMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SaleOfStockNameOfTransactionDomain_f8d05952-ef7f-4a2d-b51f-ad61947760ee" xlink:to="loc_eose_AtTheMarketProgramMember_9f868766-6ac1-4846-bd65-545d2fd82a71" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrivatePlacementMember_f41db1ff-e9da-446c-b26e-849aad74a5fe" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PrivatePlacementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SaleOfStockNameOfTransactionDomain_f8d05952-ef7f-4a2d-b51f-ad61947760ee" xlink:to="loc_us-gaap_PrivatePlacementMember_f41db1ff-e9da-446c-b26e-849aad74a5fe" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_6daf4e63-e828-4c55-8318-f7a319f89fbb" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncomeStatementLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_0876cdce-94b2-468f-8400-bd43ecc8fc1d" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_6daf4e63-e828-4c55-8318-f7a319f89fbb" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_6daf4e63-e828-4c55-8318-f7a319f89fbb_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_6daf4e63-e828-4c55-8318-f7a319f89fbb" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_6daf4e63-e828-4c55-8318-f7a319f89fbb_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_9ed94b60-0025-4d3b-8e22-d82d7734eb4d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_6daf4e63-e828-4c55-8318-f7a319f89fbb" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_9ed94b60-0025-4d3b-8e22-d82d7734eb4d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherOperatingIncomeExpenseMember_d6fd02e1-086e-47b7-9e99-8090fbba5fc7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherOperatingIncomeExpenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_9ed94b60-0025-4d3b-8e22-d82d7734eb4d" xlink:to="loc_us-gaap_OtherOperatingIncomeExpenseMember_d6fd02e1-086e-47b7-9e99-8090fbba5fc7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_7003a0bc-9d7a-44be-8965-a25db090a9a0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_0876cdce-94b2-468f-8400-bd43ecc8fc1d" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_7003a0bc-9d7a-44be-8965-a25db090a9a0" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_7003a0bc-9d7a-44be-8965-a25db090a9a0_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_7003a0bc-9d7a-44be-8965-a25db090a9a0" xlink:to="loc_us-gaap_EquityComponentDomain_7003a0bc-9d7a-44be-8965-a25db090a9a0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_00cccb86-f5ad-4226-bb78-fbbb9d0f0f37" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_7003a0bc-9d7a-44be-8965-a25db090a9a0" xlink:to="loc_us-gaap_EquityComponentDomain_00cccb86-f5ad-4226-bb78-fbbb9d0f0f37" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_f57fc3c3-04cb-46eb-847a-25ebb24d4966" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_00cccb86-f5ad-4226-bb78-fbbb9d0f0f37" xlink:to="loc_us-gaap_CommonStockMember_f57fc3c3-04cb-46eb-847a-25ebb24d4966" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_364620a5-07a7-4717-894e-a17e75b74669" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_0876cdce-94b2-468f-8400-bd43ecc8fc1d" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_364620a5-07a7-4717-894e-a17e75b74669" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_364620a5-07a7-4717-894e-a17e75b74669_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_364620a5-07a7-4717-894e-a17e75b74669" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_364620a5-07a7-4717-894e-a17e75b74669_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_92cfb06a-43e3-4fb3-ba04-3e45a98d24ae" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_364620a5-07a7-4717-894e-a17e75b74669" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_92cfb06a-43e3-4fb3-ba04-3e45a98d24ae" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_BlockASponsorEarnoutSharesMember_647b1265-c690-4005-b02f-7b636e5d1e86" xlink:href="eose-20220930.xsd#eose_BlockASponsorEarnoutSharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_92cfb06a-43e3-4fb3-ba04-3e45a98d24ae" xlink:to="loc_eose_BlockASponsorEarnoutSharesMember_647b1265-c690-4005-b02f-7b636e5d1e86" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_BlockBSponsorEarnoutSharesMember_037e05b2-ec41-41fd-9e2e-1d249414296f" xlink:href="eose-20220930.xsd#eose_BlockBSponsorEarnoutSharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_92cfb06a-43e3-4fb3-ba04-3e45a98d24ae" xlink:to="loc_eose_BlockBSponsorEarnoutSharesMember_037e05b2-ec41-41fd-9e2e-1d249414296f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_1d7bae54-f84e-4db1-952b-726c1a888a6a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_0876cdce-94b2-468f-8400-bd43ecc8fc1d" xlink:to="loc_us-gaap_DebtInstrumentAxis_1d7bae54-f84e-4db1-952b-726c1a888a6a" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_1d7bae54-f84e-4db1-952b-726c1a888a6a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_1d7bae54-f84e-4db1-952b-726c1a888a6a" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_1d7bae54-f84e-4db1-952b-726c1a888a6a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_8beead09-ac9c-4421-bdc6-67a04f5b82d1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_1d7bae54-f84e-4db1-952b-726c1a888a6a" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_8beead09-ac9c-4421-bdc6-67a04f5b82d1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_eose_YorkvilleConvertiblePromissoryNoteMember_594009dc-7ddb-4f56-9395-69d79a7aee49" xlink:href="eose-20220930.xsd#eose_YorkvilleConvertiblePromissoryNoteMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_8beead09-ac9c-4421-bdc6-67a04f5b82d1" xlink:to="loc_eose_YorkvilleConvertiblePromissoryNoteMember_594009dc-7ddb-4f56-9395-69d79a7aee49" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://eosenergystorage.com/role/ShareholdersDeficitEquityAntidilutiveSecuritiesDetails" xlink:type="simple" xlink:href="eose-20220930.xsd#ShareholdersDeficitEquityAntidilutiveSecuritiesDetails"/>
  <link:definitionLink xlink:role="http://eosenergystorage.com/role/ShareholdersDeficitEquityAntidilutiveSecuritiesDetails" xlink:type="extended" id="i03717bcccbfb4af8ba42172d737c6b5a_ShareholdersDeficitEquityAntidilutiveSecuritiesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockLineItems_ca97aea2-2a2f-4a87-9086-105d7ff26217" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfStockLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_0ddb3416-e150-4ee5-a5fc-b14e66fd5a9a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_ca97aea2-2a2f-4a87-9086-105d7ff26217" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_0ddb3416-e150-4ee5-a5fc-b14e66fd5a9a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfStockByClassTable_ef979190-1981-48cc-ae99-197fc38bdf38" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfStockByClassTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ClassOfStockLineItems_ca97aea2-2a2f-4a87-9086-105d7ff26217" xlink:to="loc_us-gaap_ScheduleOfStockByClassTable_ef979190-1981-48cc-ae99-197fc38bdf38" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_a33d2ff9-4405-4e1d-b121-11f3870c3241" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_ef979190-1981-48cc-ae99-197fc38bdf38" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_a33d2ff9-4405-4e1d-b121-11f3870c3241" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_a33d2ff9-4405-4e1d-b121-11f3870c3241_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_a33d2ff9-4405-4e1d-b121-11f3870c3241" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_a33d2ff9-4405-4e1d-b121-11f3870c3241_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_7d33bd60-1cc3-44c8-9c24-e66cae8eb4f8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_a33d2ff9-4405-4e1d-b121-11f3870c3241" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_7d33bd60-1cc3-44c8-9c24-e66cae8eb4f8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockCompensationPlanMember_d325113b-aeaf-4996-a53d-61d5be40f567" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockCompensationPlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_7d33bd60-1cc3-44c8-9c24-e66cae8eb4f8" xlink:to="loc_us-gaap_StockCompensationPlanMember_d325113b-aeaf-4996-a53d-61d5be40f567" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WarrantMember_341e3cbf-e6a4-43d2-91ee-8c140eabeb1a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_WarrantMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_7d33bd60-1cc3-44c8-9c24-e66cae8eb4f8" xlink:to="loc_us-gaap_WarrantMember_341e3cbf-e6a4-43d2-91ee-8c140eabeb1a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConvertibleDebtSecuritiesMember_975ea349-709c-4c4e-aab8-9f000215a5b9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ConvertibleDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_7d33bd60-1cc3-44c8-9c24-e66cae8eb4f8" xlink:to="loc_us-gaap_ConvertibleDebtSecuritiesMember_975ea349-709c-4c4e-aab8-9f000215a5b9" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fasb.org/us-gaap/role/eedm/ExtensibleEnumerationLists" xlink:type="simple" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-roles-2022.xsd#eedm"/>
  <link:definitionLink xlink:role="http://fasb.org/us-gaap/role/eedm/ExtensibleEnumerationLists" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsAbstract" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AssetsAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization" xlink:type="arc" order="0"/>
  </link:definitionLink>
</link:linkbase>
