A Compact Large-Current Equalizer Based on Flyback Conversion for Large-Scale Battery Packs

The equalizer can greatly improve the consistency of the series-connected battery string, which has been widely used in the field of electric vehicles. However, the existing equalization topology suffers from the disadvantages of slow equalization, large size, and complex control. Therefore, a compact equalization topology is proposed based on flyback conversion. Distinguishing from the traditional flyback conversion topology, the proposed equalizer divides the series-connected battery cells into odd and even groups. The neighboring battery cells share a pair of mosfets, which greatly reduces the number of switches and costs. Moreover, the proposed equalizer has both equalization and charge equalization modes, which can be flexibly applied in different situations. An experimental prototype is designed for 12-cell large-capacity batteries. The experimental results show that the peak equalization current reaches 10 A, which is five times higher than the traditional active equalization topology. The voltage difference is less than 5 mV after equalization. Compared with the existing equalization topologies, the proposed equalizer has a smaller size, faster equalization speed, and optional equalization modes, which can be applied to large-scale battery pack scenarios.