The novel state of charge estimation method for lithium battery using sliding mode observer

In this paper, a new state of charge estimation method for lithium battery has been presented. Contrary to the conventional methods which use complicated battery modeling, a simple resistor–capacitor battery model was used in order to reduce calculation time and system resource. Modeling errors caused by the simple model are compensated by the sliding mode observer. The structure of the proposed system is simple, but it shows robust control property against modeling errors and uncertainties. The state equation for battery model and the systematic design approach for sliding mode observer also have been presented. The convergence of proposed observer has been proved by the Lyapunov inequality equation and the performance of system has been verified by the sequence of urban dynamometer driving schedule test. The test results show the proposed observer system has robust tracking performance with reduced calculation time under the real driving environments.