Abstract: A battery heater uses the internal resistance of the battery as the battery heating element. In one embodiment, a DC battery charger and a programmable battery load, is used in a closed loop temperature control system. In another embodiment, a DC battery charger and a resistor or small auxiliary battery heater, is used in a closed loop temperature control system. The programmable load or the small auxiliary battery heater, is enabled during full charge, low temperature conditions. The resistor or small auxiliary heater serves to both heat the battery and draw down the battery charge. In yet another embodiment, an AC heater power supply and a DC battery charger, is coupled to the battery in a closed loop temperature control system.