A battery warm up system, comprising: an open signal receiving unit to receive a door open signal related to operation of the vehicle performed before the user gets in the vehicle; a temperature measuring unit to measure a temperature of a battery pack connected to a starter of the vehicle; a battery state measuring unit to measure a state of charge, SOC, of each of a plurality of battery modules constituting the battery pack; a forced discharging circuit unit to force a certain battery module among the plurality of battery modules to be discharged in response to a forced discharging start signal, a balancing unit to balance the SOC of each battery module by discharging the remaining battery modules, except the battery module forcibly discharged, in response to a balancing start signal, wherein the forced discharging circuit unit and the balancing unit comprise a forced discharging switch connected between both ends of a certain battery module among the battery modules to perform a switch ON/OFF operation in response to the forced discharging and balancing signal and a control unit, and characterized in that the control unit is configured to output the forced discharging start signal to create a SOC difference between the plurality of battery modules when the door open signal is received by the open signal receiving unit and the temperature measured by the temperature measuring unit is lower than a first reference temperature, and output the balancing start signal when the SOC difference between the plurality of battery modules reaches a set first reference amount an open signal receiving unit to receive a door open signal related to operation of the vehicle performed before the user gets in the vehicle; a temperature measuring unit to measure a temperature of a battery pack connected to a starter of the vehicle; a battery state measuring unit to measure a state of charge, SOC, of each of a plurality of battery modules constituting the battery pack; a forced discharging circuit unit to force a certain battery module among the plurality of battery modules to be discharged in response to a forced discharging start signal, a balancing unit to balance the SOC of each battery module by discharging the remaining battery modules, except the battery module forcibly discharged, in response to a balancing start signal, wherein the forced discharging circuit unit and the balancing unit comprise a forced discharging switch connected between both ends of a certain battery module among the battery modules to perform a switch ON/OFF operation in response to the forced discharging and balancing signal and a control unit, and characterized in that the control unit is configured to output the forced discharging start signal to create a SOC difference between the plurality of battery modules when the door open signal is received by the open signal receiving unit and the temperature measured by the temperature measuring unit is lower than a first reference temperature, and output the balancing start signal when the SOC difference between the plurality of battery modules reaches a set first reference amount the plurality of battery modules when the door open signal is received by the open signal receiving unit and the temperature measured by the temperature measuring unit is lower than a first reference temperature, and output the balancing start signal when the SOC difference between the plurality of battery modules reaches a set first reference amount