Method for heating a high voltage vehicle battery

A battery heating system for use with a vehicle, comprising:

• a power supply having an input and an output, the power supply input receives high voltage electrical power from an external power source located outside of the vehicle and the power supply output provides low voltage electrical power;
• a low voltage vehicle battery having an output, the low voltage vehicle battery output provides low voltage electrical power;
• a battery heater having an input, the battery heater input is selectively coupled to the power supply output when the power supply input is connected to the external power source and battery heating is needed and the battery heater input is selectively coupled to the low voltage vehicle battery output when the power supply input is disconnected from the external power source and battery heating is needed;
• and
• a high voltage vehicle battery being at least partially used for vehicle propulsion, wherein the battery heater is thermally coupled to the high voltage vehicle battery and the battery heater heats the high voltage vehicle battery with electrical power from the power supply when the power supply input is connected to the external power source, and the battery heater heats the high voltage vehicle battery with electrical power from the low voltage vehicle battery when the vehicle is being driven and while a temperature of the high voltage vehicle battery is below a target temperature.

A method for heating a vehicle battery that is at least partially used for vehicle propulsion, comprising the steps of:

• (a) determining if a battery heating system is plugged into an external power source located outside of the vehicle, wherein the battery heating system includes a switch, a battery heater, and a vehicle battery;
• (b) if the battery heating system is coupled to the external power source, then providing electrical power from the external power source to the battery heater through the switch in a first switch state;
• (c) if the battery heating system is decoupled from the external power source, then providing electrical power from an internal power source to the battery heater through the switch in a second switch state, wherein the internal power source is separate from the vehicle battery;
• and
• (d) using the battery heater to heat the vehicle battery with electrical power from the external power source when the switch is in the first switch state, and using the battery heater to heat the vehicle battery with electrical power from the separate internal power source when the switch is in the second switch state and the vehicle is being driven while a temperature of the high voltage vehicle battery is below a target temperature.