Disclosed are a system and a method of managing a battery by using a balancing battery. The system for managing a battery includes: a battery unit which includes a plurality of battery modules and provides electric energy to an electronic device; a cooling fan which adjusts a flow rate of a fluid flowing into the battery unit; a fan control circuit which controls an operation of the cooling fan; and a balancing battery which performs balancing of the plurality of battery modules by supplying electric energy to one or more of the plurality of battery modules and charging the one or more battery modules, or receiving electric energy from one or more of the plurality of battery modules, and supplies electric energy to the cooling fan under a control of the fan control circuit.