As second-life battery applications continue to grow across Europe, so does the need for robust safety investigation and accountability mechanisms. Repurposed lithium-ion batteries are increasingly used in stationary energy storage systems, where they support renewable integration and grid stability.
However, these batteries come with a history. Unlike new systems, second-life batteries have already experienced years of use, degradation and varying operating conditions. When a failure occurs, especially a fire, determining the root cause becomes significantly more complex.
This is where the Digital Battery Passport (DBP), introduced under Regulation (EU) 2023/1542, can play a critical role. By preserving structured lifecycle data, the DBP enables forensic analysis that goes beyond surface-level investigation and supports evidence-based conclusions.
Why Second-Life Batteries Require Deeper Investigation
Second-life batteries are typically repurposed after their capacity drops below thresholds required for electric vehicles. Although they may still perform adequately in less demanding applications, their internal condition is often more variable.
Factors such as previous fast charging, thermal stress or uneven degradation can influence how these batteries behave in new environments. When a fire or failure occurs, it is rarely the result of a single factor. Instead, it is usually the outcome of cumulative stress over time combined with current operating conditions.
The International Energy Agency highlights the growing role of second-life batteries in energy systems, while also noting the importance of safety and lifecycle management as deployment increases.
Without access to historical data, investigators are left with incomplete information, making it difficult to determine responsibility or prevent future incidents.
Understanding Battery Fire Root Causes
Battery fires are often linked to thermal runaway, a process in which internal reactions lead to rapid temperature rise and the release of flammable gases.
Thermal runaway can be triggered by internal short circuits, uncontrollable temperature increase due to internal failures, overcharging, external heating, as well as physical damage. Once started, it can cause a chain reaction affecting the neighbouring cells, leading to system-level failure.
In second-life applications, additional factors may contribute. These include mismatched cells within repurposed packs, inadequate system integration, or operating conditions that differ from the battery’s original design parameters.
Identifying which of these factors played a decisive role requires detailed and reliable data.
The Role Of DBP Logs In Forensic Analysis
The Digital Battery Passport provides a structured and traceable record of a battery’s lifecycle. Under Regulation (EU) 2023/1542, batteries placed on the EU market must include accessible, machine-readable data covering performance, safety and traceability.
For forensic analysis, this data becomes invaluable. DBP logs can include historical usage patterns, maintenance records, safety events and operational conditions.
When a fire occurs, investigators can use these logs to reconstruct the sequence of events leading up to the incident. Instead of relying solely on physical inspection after damage has occurred, they can analyse:
- Temperature trends before the event
- Charging and discharging behaviour
- Recorded fault codes or system alerts
- Evidence of previous abnormal conditions
This allows for a more precise understanding of what happened and why.
Reconstructing The Timeline Of Failure
One of the key advantages of DBP logs is the ability to rebuild a timeline. Fires often destroy physical evidence, making post-incident analysis difficult. Digital records, however, remain intact if stored securely.
By analysing time-stamped data, investigators can identify early warning signs that may have been missed. For example, repeated high-temperature events or irregular voltage behaviour could indicate underlying instability.
This chronological approach helps distinguish between immediate triggers and long-term degradation. It also supports more accurate attribution of responsibility, whether related to manufacturing, repurposing, system integration or operation.
Improving Accountability Across The Value Chain
Second-life battery ecosystems involve multiple stakeholders, including original manufacturers, repurposing companies, system integrators and operators. When an incident occurs, determining responsibility can be challenging.
DBP logs introduce a level of transparency that supports fair and evidence-based accountability. Each stage of the battery’s lifecycle can be documented, creating a continuous record of how the battery has been handled and used.
This transparency is aligned with the EU Battery Regulation’s emphasis on traceability and lifecycle data accessibility.
With clear records, disputes can be resolved more efficiently, and lessons learned can be shared across the industry.
Supporting Prevention Through Data Insights
Forensic analysis is not only about understanding past incidents. It is also about preventing future ones.
By analysing DBP data across multiple cases, patterns can emerge that highlight common risk factors. These insights can inform improvements in battery design, repurposing practices and operational guidelines.
For example, if data consistently shows that certain temperature thresholds or usage patterns precede failures, these can be used to refine safety limits and monitoring systems.
This shift from reactive investigation to proactive risk management is a key benefit of digital lifecycle data.
Challenges In Using DBP Data For Forensics
While the potential is significant, there are challenges to address. Data completeness and accuracy are critical. If logs are inconsistent or incomplete, conclusions may be unreliable.
There are also considerations around data access and privacy. Sensitive operational data must be protected while still being available to authorised investigators.
Standardisation is another important factor. Consistent data formats and definitions are needed to ensure that information can be interpreted correctly across different systems and stakeholders.
How BASE Enables Data-Driven Forensic Capabilities
At BASE, we recognise that the value of the Digital Battery Passport extends beyond compliance. It provides a foundation for deeper insights into battery performance, safety and lifecycle behaviour.
Our Digital Battery Passport framework supports structured, interoperable data capture and secure access mechanisms that enable reliable analysis across the battery lifecycle. By ensuring that key operational and safety data is preserved and accessible, BASE helps stakeholders conduct more accurate forensic investigations.
Through pilot implementations and collaboration with industry partners, BASE contributes to building a more transparent and accountable battery ecosystem where incidents can be understood and prevented more effectively.
Looking Ahead
As second-life battery applications continue to expand, the ability to investigate and understand failures will become increasingly important. Fires and safety incidents, while relatively rare, can have significant consequences for trust and adoption.
Digital Battery Passports offer a powerful tool for improving forensic analysis. By linking historical data with real-world events, they enable a clearer understanding of root causes and support better decision-making across the value chain.
Organisations that invest in robust data systems today will be better equipped to manage risk, enhance safety and support the long-term growth of second-life battery applications.
The BASE project has received funding from the Horizon Europe Framework Programme (HORIZON) Research and Innovation Actions under grant agreement No. 101157200.
References
EU Battery Regulation (Regulation EU 2023/1542):
https://eur-lex.europa.eu/eli/reg/2023/1542/oj
EU Battery Regulation Detailed Text: https://eur-lex.europa.eu/eli/reg/2023/1542/2023-07-28/eng
International Energy Agency – Global EV Outlook 2023: https://www.iea.org/reports/global-ev-outlook-2023
U.S. Department of Energy – Energy Storage Safety Strategic Plan: https://www.energy.gov/sites/default/files/2024-05/EED_2827_FIG_SafetyStrategy%20240505v2.pdf
BASE Project – Predicting Thermal Runaway with Digital Battery Passport: https://base-batterypassport.com/blog/technology-7/predicting-thermal-runaway-with-digital-battery-passport-94