Non-dissipative equalization with voltage-difference based on FPGA for lithium-ion battery

As power source of electric vehicles (EVs), the inconsistency of lithium-ion battery directly affects the performance and safety of EVs. A non-dissipative equalization scheme is proposed to improve the inconsistency in this paper. The bidirectional equalization circuit based on inductance as energy transferring media is designed to reduce the loss of equalization energy and improve the utilization of capacity for lithium-ion battery. To facilitate the implementation of battery equalization, the equalization strategy with voltage-difference control method is selected. Then the equalization system is built to demonstrate the feasibility of equalization scheme in MATLAB/Simulink. Finally, on the basis of field programmable gate array (FPGA), the actual hardware circuit is designed, and the equalization experiment of 4 LiFePO4 battery cells is carried out. The final range of charging voltage is 0.011V and the final standard deviation of charging voltage is 0.41%. The experimental results show that the cells actual voltage differences can converge to an acceptable range and verify the validity of the proposed non-dissipative equalization scheme.