Multi-Winding Equalization Technique for Lithium Ion Batteries for Electrical Vehicles

The concept of active cell equalizing method based on multi-winding transformer balancing for Lithium Ion (Li-ion) batteries is presented in this paper. In a battery pack, voltage differences exist between cells due to charging and discharging process thus, a battery management system (BMS) is required to ensure that all battery cells are equally charged or discharged. An equalizing method is essential to achieve the best performance. A number of cell balancing method have been presented. Among them multi-winding transformer balancing method has fast equalization time, and is easy to control. As compared to the conventional multi-winding transformer (Fly back structure) that uses diodes and requires air gap, this method (Forward) uses MOSFETs as a switch in the output and uses single phase inverter in the input. Fast equalization, easy to control, high efficiency and easy isolation are some of its features. The simulation results are accomplished to demonstrate the viability of the system.