Battery pack and balancing method of battery cells

摘要

A balancing method for a battery pack includes balancing battery cells near an end of discharge. A deep discharge of the battery cells can be prevented without using an overdischarge control unit. One battery cell balancing method includes: a balancing check condition determination step for determining whether or not a maximum voltage out of voltages of the battery cells is smaller than a reference voltage; a balancing start condition determination step for determining whether or not a residual capacity difference or voltage difference between the individual battery cells exceeds a reference value; a balancing time calculation step for calculating a balancing time for discharging the battery cell that exceeds the reference value; and a balancing operation step for discharging the selected battery cell when the battery cells are under charge or are at rest or when a discharge current of the battery cells is smaller than a reference current.