Switched Equalization with Zero-Voltage Switching for Series Battery Pack

The imbalance in cells leads to a decrease in the performance and life of series lithium-ion battery pack, especially in electric vehicles (EVs) field. This paper adopts a switched equalization technology with zero -voltage switching (ZVS) to eliminate the imbalance. The proposed technology transfers excess energy from cell to pack. Furthermore, the MOSFET switches of switch array can be drive by battery cell for a cheap implementation. The proposed fly-back circuit achieves ZVS when MOSFETs turn off, and recovers the energy of leakage inductance, simultaneously. Hence, the losses on MOSFET and transform can reduce, and the volume of fly-back circuit may also decrease. The paper details how to design the fly-back circuit, and verifies the technology by experiments.