A Fusion Method of Series-Connected Batteries State-of-Health Estimation and Balancing Strategy Applied to Multi-Cell-to-Multi-Cell Equalizer

Abstract

Lithium-ion battery is the most commonly used energy storage tool at present. In the process of using, the aged batteries reduce the battery endurance and cause an explosion. Therefore, it is necessary to estimate the state-of-health (SOH) and achieve battery equalization. This paper proposes a method for SOH estimations and balancing strategy based on balancing voltages and balancing current expectations. The real-time voltage differences are employed to get the balancing current expectations. In addition, the RMS of current can reach the current expectation by controlling the phase angle of hardware circuit, to realize the rapid convergence of battery voltage. With the ratio of cell-to-cell balancing current expectation, the SOH estimations of all cells within a series-connected battery pack can be obtained. Results show the SOH estimations relative error can be well controlled within 2%, and it takes less estimated time.