Researchers at Graz University of Technology have made significant strides in improving the assessment of discarded electric vehicle batteries for potential reuse in stationary power storage units. The current method relies on two criteria – reduced charging capacity and increased internal resistance – which the researchers deem insufficient for determining second-life use.
The team analyzed lithium-ion cells used in vehicles under real-life conditions and compared them with new specimens in laboratory settings. They conducted reproducible charging and discharging cycles, recording 31 different measured values to assess the batteries’ aging condition. From this, 13 indicators were identified as meaningful, including charging and discharging capacity, temperature differences between poles during charging, and relaxation behavior post-charging.
Jörg Moser, Head of the Battery Safety Centre Graz, stated, “Based on these indicators, we can draw conclusions about the ageing status of lithium-ion batteries and draw initial conclusions about different usage profiles without having to rely on data protection-critical information about the usage history of the batteries.”
However, the researchers caution that even with these advancements, the safety status of the batteries must be assessed before reuse. Chemical changes during their first life in vehicles can impact their safe use. Christian Ellersdorfer, leading the SafeLIB project, emphasized the need to understand battery cells and their processes to qualify them in terms of safety behavior.
The researchers also highlighted the need for ongoing adaptation of evaluation methods due to evolving battery technology. They also emphasized the importance of considering economic viability and legal issues related to second-life applications, including data protection, warranty, and liability.
