An Online Estimation Algorithm of State-of-Charge of Lithium-Ion Batteries

An online estimation algorithm of State-of-Charge (SoC) of Lithium-ion (Li-ion) batteries based on terminal sliding mode (TSM) observer technique is proposed. A first-order RC equivalent circuit model is utilized to describe the dynamical behaviors of Li-ion batteries. A sliding mode observer is developed to track the states of the Li-ion batteries and the control signal of the observer is used to estimate the SoC of a Li-ion battery accurately. The proposed observer is robust to internal parameter uncertainties of the battery model, and the environment changes. Compared with the traditional sliding mode observers, the proposed sliding mode observer has the continuous control signal, which can be used for the SoC estimation algorithm directly. The proposed method has been verified by the estimation results and the effectiveness has benn demonstrated.