An Improved Buck-Boost Circuit Equalization Method for Series Connected Battery Packs

Series-connected lithium-ion battery packs have inherent divergence of cell state of charge (SOC) and the differences will be further enlarged with repeated charging and discharging cycles, which will reduce the available capacity and lifetime. In this paper, an improved equalization circuit is proposed based on the buck-boost principle and the control simulation is implemented. The lithium-ion battery model is established and a series-connected lithium-ion battery pack balancing system with SOC as the balancing target is built. Simulation verification and comparative analysis show that comparing with the traditional buck-boost circuit, the improved design without adding any components is faster and much efficient: the time to realize the equalization is reduced and the energy utilization rate is improved.