A review of active cell balancing methods in electric vehicles

The high energy density and modularity of Lithium-ion (Li-ion) batteries make them ideal for electric vehicles (EVs). However, in series-connected battery packs, cell imbalance emerges as a critical challenge, resulting in voltage variations, accelerated aging, safety concerns, and reduced usable capacity. This paper systematically compares and evaluates active cell balancing methods, presenting a comparative analysis to provide a suitable selection for EVs. Furthermore, it offers a classification of DC-DC converter-based balancing circuits, distinguishing between non-isolated and isolated configurations based on their electrical isolation characteristics, analyzing their trade-offs in efficiency, cost, and balancing speed. To validate these topologies, four DC-DC converter-based balancing structures are modeled and simulated in MATLAB/Simulink. The simulation results provide a comparative performance analysis, with particular emphasis on balancing speed and current ripple characteristics. Based on these findings, the paper discusses the relative characteristics of the four methods. Finally potential research directions for optimizing cell balancing techniques are outlined to guide future studies in this field.