Research on Active Balance Strategy of Retired Lithium Batteries

In order to solve the obvious inconsistency problem of retired lithium batteries in electric vehicles, this paper designs an active equalization system circuit based on a bidirectional flyback equalization topology. Using unscented Kalman filter (UKF) to estimate the state of charge (SOC), the SOC-based, voltage-based, and SOC and voltage-based two-variable equalization strategies are designed, a system simulation model is built, and the three equalization strategies are compared and verified. The proposed balancing strategy meets the requirements of retired battery balancing control, and the SOC-based balancing strategy has the fastest balancing speed.