Abstract:A battery pack in series charging, the increase of battery use time and charge and discharge times, the performance difference gradually increases, this will cause individual batteries to overcharge, and the phenomenon of individual battery undercharged with power. This is a great harm to the battery and there are security risks. Designed a device for use in a battery pack of powered UPS device, used to protect a series charge, for each battery not to have the overcharging. Each battery is charged with a voltage limiting charge, thus, the final charging voltage of each battery can be basically kept the consistent to give full play to the efficiency of the battery and to protect the battery from overcharging or undervoltage. The control equipment after a certain period of time to run the test, the effect is good it can meet the requirement of equalizing charging for battery pack of power UPS device.