Sustainable repurposing of EV batteries: A methodology for certification in the EU

The transition to electric mobility is essential for sustainable development, driving a sharp rise in battery use for electric vehicles (EVs). Once these batteries have reached the end of their first vehicle life cycle (1 st EOL), they are no longer suitable for vehicle traction, but can be repurposed for less demanding applications before being recycled. This approach prolongs battery lifespan while yielding measurable environmental and economic benefits. However, the widespread repurposing of these batteries is limited by a lack of standardised certification procedures. This study proposes a certification methodology for second-life lithium-ion batteries, based on Regulation (EU) 2023/1542 and the UL 1974 standard. The methodology comprises eight key steps to ensure safety, performance, and regulatory compliance for CE marking in the EU. A key step in the methodology is performance testing, which includes BMS functionality checks, open-circuit voltage, insulation resistance, capacity (via charge/discharge cycles), internal resistance, and self-discharge tests. These tests assess the battery’s state of health (SoH) and state of charge (SoC), enabling sorting and repurposing. A case study of a BMW plug-in hybrid battery module shows testing costs of 57.3–57.4 €/kWh, indicating economic feasibility. This work supports the safe and sustainable integration of repurposed EV batteries into new energy applications.