Hybrid Battery Balancing System for Electric Drive Vehicles

In electric vehicles, cell and module voltage equalization plays a vital role in Battery Management System (BMS). The capacity, temperature, and aging imbalances in the cells and modules of electric vehicles battery packs restrict the amount of power that can be delivered to the vehicle. Spurred by this issue, we propose a new class of battery balancing systems, called hybrid balancing, capable of simultaneously equalizing battery capacity while enabling cost-effectiveness of cell-level passive balancing and module-level active balancing, modules consist of a number of cells connected in series, with cell-level passive balancing performed in a module, together with the module level switched capacitor that performs active balancing among the modules. The strategy is called hybrid balancing because it pursues goals beyond conventional state-of-charge equalization, including temperature and power capability equalization, and minimization of energy losses. Design details and MATLAB Simulink simulation results are provided for a hybrid balancing system implemented on a lithium-ion battery pack.