This paper proposes an equalizer for lithium-ion battery and two different balancing strategies are used according to battery charging and discharging states.In battery charging state

the battery cell with the highest energy is balanced and discharged by the equalizer to improve charge capacity of the whole battery pack.In battery discharging state

the battery cell with the lowest energy is balanced and charged by the equalizer to improve discharge capacity of the whole battery pack.The balancing circuit uses an inductor as the energy storage element and the equivalent balancing circuits are the typical boost-buck chopper circuit and the buck chopper circuit

further the balancing current is controllable and adjustable.This paper draws working principle and control strategies of the equalizer.Furthermore the simulation and actual balancing experiments have been completed.Finally

the feasibility of the equalizer suggested in this paper is verified according to the balancing experimental results.