US Patent 10361571 Battery pack

A battery pack includes first and second main relays connected between respective terminals of the battery and a load, a temperature variable resistor connected in parallel to the second main relay, a heating coil adjacent to the temperature variable resistor, and first and second switches respectively connected between a power source and coils of the first and second main relays. A third switch is connected between the power source and the heating coil. A controller to control on/off states of the first, second, and third switches.