A novel multiple-battery charger with flying-capacitor three-level converter and four-stage charging method for fast charging

To achieve charging multiple batteries at the same time, and grasp the charging mode transition timing accurately, this paper proposes a new charge method for multiple batteries which is a four-stage Li-ion battery charger with flying-capacitor three-level converter. Since three-level converter can generate multiple level voltages, the distortion of power source and electromagnetic interference (EMI) will be significantly reduced, and the voltage stress will also be decreased. By connecting batteries in parallel, it will easily monitor the charge voltage and current of every battery, and the charger realizes battery voltage balance by adjusting the voltage and current. The charging process adds pulse current mode. The charging mode transition timing could be grasped exactly since pulse current which will remove the effect of the parasitic resistor. Therefore, the total time will be reduced, and the overall charge speed will be faster.