Self heating of batteries at low temperatures

A battery powered computer system comprising:

• a host device;
• and
• a rechargeable battery pack coupled to the host device, the battery pack capable of providing power to the host device, the battery pack including:
• a rechargeable battery having a positive terminal and a negative terminal;
• a heater circuit, the heater circuit coupled to the rechargeable battery and operable to receive current from the rechargeable battery;
• a controller coupled to the heater circuit;
• and
• a temperature monitoring circuit coupled to the controller, the temperature monitoring circuit being capable of measuring a temperature of the battery pack and providing a temperature indication to the controller, the controller causing the heater circuit to heat the controller based upon the indication.

A method of protecting a rechargeable battery pack comprising:

• providing a rechargeable battery pack including a rechargeable battery, a temperature monitoring circuit, a heater circuit operable to receive current from the rechargeable battery, and a controller;
• measuring a temperature of the rechargeable battery with the temperature monitoring circuit;
• comparing the measured temperature with a threshold temperature to obtain a comparison result;
• and
• activating the heater circuit based upon the comparison result.

An apparatus for protecting a rechargeable battery pack comprising:

• a heater circuit operable to receive current from the rechargeable battery pack;
• a controller coupled to the heater circuit;
• and
• a temperature monitoring circuit coupled to the controller, the temperature monitoring circuit being capable of measuring a temperature of the battery pack and providing a temperature indication, the controller causing the heater circuit to heat the controller based upon the indication.