US Patent 9083065 Self heating battery system

A battery self heating system for batteries that experience battery impedance or internal battery resistance when temperature drops. The system comprises an energy storage element applied to the battery terminals to draw energy from the battery. The energy is stored in a magnetic or capacitive storage device. The system is self-resonant so that energy transfer from the storage device to the battery will occur at a frequency and load level that is compatible with the current state of the battery. Internal heating of the battery is accomplished by a cycle comprising the out flux and influx of energy through the impedance of the battery. Energy losses due to battery impedance are converted to heat thereby heating the battery internally.