A Bi-directional Charge Equalization Circuit for Series-connected Batteries

For both charging and discharging series-connected batteries, charge equalization is necessary in order not to influence battery cycle life. This paper proposes a bi-directional charge equalization circuit for both charging and discharging series-connected batteries. In addition to balance charging and discharging, this circuit can improve the output voltage regulation to resist the battery voltage reduction when SOC (state of charge) is low. A DSP processor is adopted to perform the control tasks. Experiments were implemented to verify the feasibility of this circuit.