Voltage equalizer for li-ion battery string using LC series resonance

This paper proposes voltage equalizer for lithium-ion battery string. Proposed equalizer uses LC resonant tank for energy transfer between battery cells. LC resonant tank is connected to the cells by switch network and can store and release energy from any cell in the battery string. Therefore energy can be transferred from strong cell to weak cell directly, which is effective for both of top and bottom balancing. In order to improve balancing performance, adjustable speed structure is employed. Prototype was implemented for 5 cell lithium-ion battery string. Experimental results showed that proposed circuit is suitable for battery cell balancing.