Battery warm up system and method for warming up battery using the same

1. A battery warm up system, comprising:

an open signal receiving unit to receive a door open signal for opening a door of a 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 control unit to output a forced discharging start signal to create an SOC difference between a plurality of battery modules by referring to information associated with the temperature measured by the temperature measuring unit when the door open signal is received by the open signal receiving unit, and output a balancing start signal by referring to the SOC of each of the plurality of battery modules;

a forced discharging circuit to force at least one battery module but less than all battery modules among the plurality of battery modules to transmit current through a resistor in the forced discharging circuit in response to the forced discharging start signal to create the SOC difference between the plurality of battery modules; and

a balancing unit to balance the SOC of each battery module in response to the balancing start signal,

wherein the forced discharging circuit consists essentially of a switch and a resistor in parallel with each battery module, the switch being in series with the resistor.

2. The battery warm up system according to claim 1 , wherein the control unit outputs the discharging start signal when the measured temperature of the battery pack is lower than a first reference temperature.

3. The battery warm up system according to claim 2 , wherein the control unit outputs a forced discharging end signal when the temperature of the battery pack reaches a second reference temperature or a discharge amount reaches a set reference discharge amount by the forced discharging.

4. The battery warm up system according to claim 3 , wherein the forced discharging circuit comprises 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 start signal and the forced discharging end signal.

5. The battery warm up system according to claim 1 , wherein the forced discharging circuit forces, in response to the forced discharging start signal, a certain battery modules among the plurality of battery modules to be discharged simultaneously or sequentially in a set order.

6. The battery warm up system according to claim 1 , wherein the battery state measuring unit comprises a voltage sensor to measure a voltage of the battery module.

7. The battery warm up system according to claim 6 , wherein the battery state measuring unit further comprises an SOC calculating unit to calculate an SOC of the battery module using information including a voltage value sensed by the voltage sensor.

8. The battery warm up system according to claim 6 , wherein the control unit calculates an SOC of the battery module using information including a voltage value sensed by the voltage sensor.

9. The battery warm up system according to claim 1 , wherein the balancing unit balances the SOC by forcing a remaining battery module to be discharged except the forcibly discharged certain battery module.

10. A power supply system for vehicles, comprising:

a battery warm up system defined in claim 1 ; and

a battery pack connected to the battery warm up system.

11. A vehicle comprising:

a power supply system for vehicles defined in claim 10 ; and

a starter to receive power needed for start-up from the battery pack.

12. A method for warming up a battery, the method comprising:

determining whether a door open signal for opening a door of a vehicle is received;

comparing a temperature of a battery pack to a set first reference temperature;

creating an SOC difference between a plurality of battery modules by outputting a forced discharging start signal when the door open signal is received and the temperature of the battery pack is lower than the first reference temperature by transmitting current from at least one battery module but less than all battery modules among the plurality of battery modules through a resistor in parallel with the at least one battery module in a forced discharging circuit provided for each battery module by closing a switch in series with the resistor;

outputting a balancing start signal when an SOC between the plurality of battery modules constituting the battery pack becomes imbalanced due to discharging of a at least one battery module but less than all battery modules among the plurality of battery modules in response to the output of the balancing start signal.

13. The method for warming up a battery according to claim 12 , further comprising:

outputting a forced discharging end signal when the temperature of the battery pack reaches a second reference temperature or a discharge amount of a battery module constituting the battery pack reaches a set reference discharge amount in response to the output of the forced discharging start signal.