Estimating the State of Charge of Lithium-ion Battery based on Sliding Mode Observer

Battery management system (BMS) requires an accurate prediction of state of charge (SOC) of electric vehicles (EVs). In this paper, a first-order RC network equivalent circuit battery model with the hysteresis characteristic of Lithium-ion battery is built up. The parameters of battery equivalent circuit model (BECM) is identified. And then, we design a sliding mode observer (SMO) to estimate SOC of batteries in EVs. The robustness and observability of the SMO of SOC estimation are proved. Matlab/Simulink and AMESim co-simulation method is adopted to evaluate the performance of the presented algorithm. The simulation results show that the SOC estimation error is less than 3%.