Assessment of spent EV batteries for second-life application

Abstract

Electric vehicle (EV) batteries typically retained around 70- 80% of their initial capacity at the end of their automotive life. The first batches EV batteries are hitting their retirement age and around 3 million used battery packs will be coming out from EV annually which represent around 108 GWh. Automotive companies and OEM have announced numerous projects and business models for second-life batteries, such as the stationary energy storage system (ESS) to extract additional services and revenue in post automotive life with cross-cutting benefits. The potential of second-life batteries lies in their state of health (SoH) or remaining useful life. To enable this market for second use batteries, it is necessary to demonstrate the capability of such batteries in real-world scenarios and validating the longevity of these batteries in this application is critical. This paper characterises three selected Nissan Leaf Cells/Modules disassemble from 24 KW Nissan Leaf pack that reach an end of life (EoL). The modules are tested individually to provide insight into the variation in degradation across a single battery pack and also establish the available energy at EoL via Hybrid pulse power characterization (HPPC). The result shows three data points of capacity and Ohmic resistance. Furthermore, the batteries achieved the power density of 700 W/Kg/300 W/Kg during discharge/regen in the working regions from 100% to 30% and /80% to 20% DOD respectively. Besides, the HPPC micro cycle discriminates between the strong and weak battery in 120 s.