For use when charging and after charging your Li-Po battery pack. Keeps battery pack warm for a lower internal resistance, and higher voltage on the track. This is the trick all the serious team racers have been doing. Keeps batteries at a constant voltage. Element wraps around pack for heating on all sides. Removable heat sleeve maybe used as tire warmer and allows case to be used to store battery pack. Works off a 12 volt battery or power supply. Heat pulses to keep temperature constant.