Estimation of Li-ion battery State of Charge based on extended Kalman filtering

In order to obtain the accurate estimation of SOC (State of Charge), this article is based upon the 2-order RC equivalent circuit model of Li-ion battery. The nonlinear relationship between OCV (Open Circuit Voltage) and SOC of the battery is derived from a rapid test. Depending on the parameter identification of the equivalent circuit model, which the least square method is applied to, the extended Kalman filter for the estimation of SOC can be carried out. The final simulations and the result of the experiments show that the extended Kalman filter can reduce the influence of white noise and make the accuracy of SOC estimation within 1.4%.