A star-structured switched-capacitor equalizer for series-connected battery strings

A series of star-structured switched-capacitor equalizers (SSSCEs) are proposed to achieve high balancing speed and efficiency independent of the cell number and the cell voltage distribution without significant influences on the size, cost, control, and reliability compared with the classical switched-capacitor equalizer (CSCE). The proposed topologies use the least MOSFETs and capacitors to achieve all the direct balancing paths between any two cells, and are the optimal switched-capacitor (SC) structures. A prototype system for four lithium-ion battery cells is set up. Experimental results show improved balancing performances with strong robustness. Moreover, the measured balancing efficiency is up to 93.1%.