Optimization of Electric Vehicle Charging for Battery Maintenance and Degradation Management

Battery management for plug-in electric vehicles (PEVs) has attracted extensive research attention, with most existing studies focusing on PEV operating conditions. However, battery maintenance during idling remains largely unexplored, under which electrochemical side reactions can cause battery degradation. The degradation rate depends on battery states, e.g., state of charge (SOC) and temperature. Considering that PEV idling accounts for the majority of the time, the accumulated degradation could have a major impact on battery and vehicle lifetime. In this article, battery maintenance during extended idling periods is investigated by utilizing a commonly available infrastructure, i.e., the charging unit. An optimal charging profile is designed to maintain the battery states under desirable conditions to minimize degradation over the idling period while still satisfying the charging energy requirement. Optimal charging profiles are obtained under different ambient temperatures and stages of battery life, showing different features due to respective dominating degradation mechanisms. Compared with the optimal charging profile, constant-current (CC) charging could result in up to 51.6% higher capacity loss, and that of (fast) CC-constant-voltage charging could be up to 12.3 times higher under circumstances over a 12-h overnight idling period. Integration/accommodation of user and grid demand is also addressed by augmenting the optimization framework.