Experimental Analysis of a Lithium-Ion Battery Pack after Long Service Life in a Conventional Electric Vehicle Considering Second-Life Applications

The mobility transformation from the classic combustion engine to the electric vehicle (EV) is the current focus of research and development. The increasing market penetration of EVs and the need for a sustainable and resource-saving energy transition make the development of second-use concepts necessary. Since the condition of the batteries after first life in an EV is mostly unknown, the batteries must be tested in or outside the vehicle before a decision can be made about re-use or recycling. For decision making, the remaining capacity and the internal resistance must be determined. Due to the unknown state of the system, the methods normally used for this must be reconsidered, as aged traction batteries behave different in comparison to new ones. Accordingly, this paper discusses the process of testing for second life (SL) applications using a conventional EV after 11 years of usage as an example. For this purpose, the classic capacitance test at various temperatures and current levels, and a modified high-pulse power characterization test (HPPC) were applied at module level. Further, conclusions on the cell behavior and reconfiguration are drawn by approximation of the characteristic voltage curve to calculate cell-to-cell capacitance differences.

Keywords: Reliability, Sustainability, Safety, Second life, Traction batteries, Condition assessment, Battery testing.

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