Battery management system and driving method for cutting off and coupling battery module from/to external device

A battery management system for controlling an operation of a secondary battery module comprising a plurality of unit batteries, the battery management system comprising:

• sensor means for sequentially measuring respective voltages of the plurality of unit batteries;
• comparator means for comparing the respective voltages of the unit batteries to a cut-off voltage range to determine whether the respective voltages are within the cut-off voltage range, and for comparing the respective voltages of the unit batteries to a recovery voltage range to determine whether the respective voltages are within the recovery voltage range;
• and
• controller means for receiving comparison results from the comparator means, for cutting off the secondary battery module from an external device when at least one unit battery from among the plurality of unit batteries is outside the cutoff voltage range, and for coupling the secondary battery module to the external device when all of the unit batteries are within the recovery voltage range.