A battery management system for optimizing the internal resistance of a battery includes a current measuring unit that measures a charge current of the battery, a memory that stores a plurality of voltage-current characteristic profiles, and a control unit that determines a reference profile from the plurality of voltage-current characteristic profiles based on a state of charge and temperature of the battery. The reference profile includes a start point, an end point, and a plurality of intermediate points disposed between the start point and the end point. The control unit determines an internal resistance of the battery, sets one of the plurality of intermediate points as a reference point, determines a reference resistance based on the reference point and the end point, and determines an optimal resistance based on the charge current, the internal resistance, the reference resistance and a predetermined upper limit of charge current.