Research on estimation of lithium-ion battery SOC for electric vehicle

Based on the analysis of factors affecting SOC and SOC algorithm, a new method to predict the state of battery was described in this paper. The working state of battery was divided into three states: standby state, transitional state, and charge-discharge state. Predicting each state by different SOC algorithm could eliminate the influence of factors affecting the value of SOC. Especially in the charge-discharge state, this method could improve the Ah counting approach by eliminating the accumulated error using the calculation of changing capacity of lithium-ion based on columbic efficiency. The test results show that this new way can increase the SOC accuracy and reach the demands of electric vehicle.