EPRI Battery Energy Storage Systems (BESS) Failure Incident Database

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The UL Lithium-Ion Battery Incident Reporting encompasses incidents caused by utility-scale, C&I, and residential BESS, as well as EVs, e-mobility, and consumer products. This database focuses exclusively on lithium ion technologies. EV FireSafe tracks EV and electric micro-mobility fires involv- ing (though not necessarily caused by) the traction battery, and categorizes incidents by cause. Both the UL Lithium-Ion Battery Incident Reporting and EV FireSafe provide statistics and figures, but do not disclose details of individual failures or sources.
There is currently no public resource that categorizes BESS incidents by cause of failure. This information would pro- vide industry-level insights on common and uncommon fail- ure modes, and would help to prioritize needed mitigation technology R&D. This knowledge is particularly important because individual incident details and root cause informa- tion are not always easily accessible, but are crucial to im- prove safety and understand risk. Failure classification can help determine the role of different components of a BESS, from controls to battery cell/module, in contributing to
an incident and in preventing future incidents. No current federal, state, or local jurisdiction requires incident report- ing. Even in cases where detailed root cause investigations are conducted, legal barriers often prevent the results from being shared publicly. New York state encouraged Original Equipment Manufacturers (OEMs) to disclose root cause analyses (RCAs) after failure incidents, but stopped short
of including a requirement for disclosure in their pending update5 to the fire code.
This report is intended to address the failure mode analysis gap by developing a classification system that is practical for both technical and non-technical stakeholders. Once cat- egorized in a standardized manner, the aggregated failure data was analyzed to better understand trends in how, why, and how infrequently BESS fail, and to provide recommen- dations for future safety improvements.
5 New York State Inter-Agency Fire Safety Working Group: Fire Code Recommendations. NYSERDA. Feb 6, 2024. https://www.nyserda. ny.gov/-/media/Project/Nyserda/Files/Programs/Energy-Storage/ Draft-New-York-State-Inter-Agency-Fire-Safety-Working-Group-Fire- Code-Recommendations.docx.
METHODOLOGY
This report relies on data from EPRI’s BESS Failure Incident Database along with findings from incident reports and root case analyses and expert interviews conducted by the authors to build robust descriptions of each event. Each incident from the database is categorized through a biaxial framework to allow for analysis of two distinct failure facets. BESS failures were classified by a) the root cause
of failure (design; manufacturing; integration, assembly & construction; or operation); and b) by the element of the BESS that experienced the failure (cell/module, controls, or balance of system). The study examines the proportion of failures sharing a root cause or responsible element, the re- lationship between root cause and the element experienc- ing failure, and the trends in failure type and rate over time. Results from this analysis will inform the industry’s efforts to optimize safety research and product development.
The BESS Failure Incident Database
EPRI’s BESS Failure Incident Database is the main source
of data for this report. The database was initiated in 2021 following the series of lithium ion BESS fires in South Korea and the Surprise, AZ, incident in the US. The database gathers information on stationary BESS failure events for commercial and industrial (C&I) and utility-scale BESS. This database defines utility-scale BESS as a system that is inter- connected to the grid, with no capacity limitations, while C&I systems could include behind-the-meter installations. Residential energy storage system failures are not tracked by this database and were not considered in this report.
It contains incidents as far back as 2011 and continues to be updated with new incidents as they occur. The focus
of the database is on occurrences that had a wider public health and safety risk or impact, rather than on operational failures where no additional risk to personnel or equipment was present or likely. EPRI defines failure incident as an oc- currence which resulted in increased safety risk, caused by a BESS system or component failure rather than an exog- enous cause of failure (e.g., wildfire impacting the BESS).
3 | EPRI White Paper 15256168
May 2024