Balancing Strategy of Lithium-ion Batteries Based on Change Rate of SOC

摘要

This paper proposes a balancing strategy to improve the balancing performance of series-connected lithiumion batteries. The key point of the proposed strategy is to control the change rate of state of charge (SOC) of different batteries to be equal so that imbalance can be prevented from emerging and expanding. With this strategy, the discrepancy of real maximum capacity in aged batteries can be mitigated and the lifespan of batteries can be prolonged. In addition, the required balancing current of the equalizer is reduced owing to reduction of SOC gap, which helps minimize the energy loss during the balancing procedure. The digital controlled Adjacent Cell to Cell (A-C2C) architecture is adopted, with which flexible and complex balancing strategies can be applied to the battery system. A balancing experimental prototype with the aged batteries was built and verified the effectiveness of the proposed balancing strategy.