Research on Lithium Battery Equalization of Electric Bicycle Based on Improved Series Buck-Boost Topology

In the field of lithium-ion battery applications, in order to meet the specific voltage usage requirements, battery packs are usually connected in series structure. However, the traditional series-connected Buck-Boost equalization topology suffers from slow equalization speed and low efficiency. In this paper, we improve the efficiency of equalization by improving the traditional series topology and introducing inter-battery pack equalization paths to overcome the limitation that equalization can only be performed between neighboring cells. The battery pack equalization strategy uses the state-of-charge (SOC) based battery as the equalization variable, and when the SOC difference within or between battery packs exceeds the preset equalization threshold, the equalization process will be initiated for both intra- and inter-groups. In order to verify the effectiveness of the proposed equalization topology and strategy, finally, the traditional series circuit model and the improved circuit model are constructed in the MATLAB/Simulink environment for the equalization simulation verification. The simulation results show that the improved equalization topology effectively improves the equalization speed and equalization efficiency compared to the traditional series topology.