Adaptive gain sliding mode observer for state of charge estimation based on combined battery equivalent circuit model in electric vehicles

An adaptive gain sliding mode observer (AGSMO) for battery state of charge (SOC) estimation based on a combined battery equivalent circuit model (CBECM) is presented. The errors convergences of the AGSMO for the SOC estimation are proved by Lyapunov stability theory. The AGSMO has a capability of compensating modeling errors caused by the parameters variation of the CBECM and minimizing chattering level in SOC estimation. The lithium-polymer battery (LiPB) is used to conduct experiments for extracting the parameters of the CBECM and verifying the effectiveness of the proposed AGSMO for the SOC estimation.