A Distributive Hybrid Cell Balancing Technique for Series-Connected Lithium-Ion Cells

As the demand for high energy density batteries has surged due to their use in transportation electrification and energy storage systems (ESS), the role of battery management systems (BMS) has become even more critical. Individual cells in a battery pack can develop imbalances in their state of charge (SOC) during charge/discharge operations, which in turn can diminish battery pack's ability to operate at its rated capacity. Therefore, cell balancing that ensures optimal performance of a battery pack becomes a critical function of the BMS. In this study, a distributive hybrid cell balancing technique is presented which incorporates both passive and active balancing strategies for optimal cell balancing based on the difference in SOC among the cells. The proposed method is designed to address imbalance in SOC more effectively and in a shorter duration compared to conventional inductor based active balancing and resistors based passive balancing. Simulations were run to validate the performance of the proposed technique during three different modes of battery operation: idle, charging, and discharging. Furthermore, a hardware prototype was also developed for practical demonstration of the proposed hybrid technique.