SOC Estimation of Battery Pack Considering the Equalization Current

The estimation of the battery state of charge (SOC) is an important part of the battery management system (BMS). The battery pack is usually composed of multiple single cells in series and parallel. Due to the inconsistency of single cell manufacturing and working conditions, it is necessary to equalize the battery pack. However, the equalization current will affect the output voltage of the battery pack, thereby disturbing the SOC estimation. In this paper, a battery pack SOC estimation algorithm that extended Kalman filter considers equalization current (EKF-EC) is suggested. The EKF-EC takes into account the influence of the equalization current on the output voltage of the battery pack during the battery pack charging and discharging, so it has achieved a higher estimation accuracy.