Empirical calendar aging model for LPF and NMC EV batteries – Romanian case study

The forecasting of large volumes of retired electric vehicle (EV) batteries has intensified the efforts of repurposing the ones with remaining usable capacity in different second-life applications, including as battery energy storage systems. This paper analyses the potential of repurposing the retired batteries of the most commercialized EV model in Romania by approximating the remaining usable capacity. An empirical calendar aging model is applied considering the chemistry, nominal usable capacity and calendar warranty period when the battery temperature is 25°C, 35°C and 45°C. Moreover, in each scenario four urban driving styles are presumed, with different values for State-of-Charge (SoC): 40%, 50%, 60% and 70%. The results show that the remaining usable capacity depends not only on chemistry, but also on stress factors like operational temperature, charging strategy and driving behaviour. The available capacity for second-life applications varies from 23.97 kWh, for best case scenario, to under 10 kWh, for intensive degradation, implying the need for a rigorous sorting methodology for retired batteries