Switching Kalman Filter for State-of-Charge Estimation of Li-ion Battery Balancing Systems

State of charge (SOC) estimation of lithium-ion batteries has been extensively studied, and most of the existing research focuses on SOC estimation of individual lithium-ion battery. In practical applications, however, lithium-ion batteries are connected to a balancing circuit to eliminate imbalances between batteries. When a balancing circuit is activated, the state space equation of its equivalent circuit will change. In this paper, we propose a switched extended Kalman filter method for SOC estimation of lithium-ion battery balance systems. The switching system model is established by combining the Li-ion battery equivalent circuit model and the switching resistance balance circuit. A switching extended Kalman filter is designed to estimate the SOC of a switching system.