A battery management system for controlling a secondary battery module which includes a plurality of unit batteries includes a sensor, a comparator and a controller. The sensor sequentially measures respective voltages of the unit batteries. The comparator compares the respective voltages of the unit batteries to a cut-off voltage range and a recovery voltage range to determine if the voltages are within the cut-off voltage range and the recovery voltage range. The controller receives comparison results from the comparator, cuts off the secondary battery module from an external device when there is at least one unit battery within the cutoff voltage range, and couples the secondary battery module to the external device when all of the unit batteries are within the recovery voltage range.