A device for thermal control of a battery system includes a heating control module electrically connected to the battery system and a conversion device configured to control power output from the battery system. The heating control module is configured to measure a current through the conversion device, the measured current provided by the battery system of a vehicle during vehicle operation or provided by an energy source during vehicle charging. The heating control module is also configured to control the conversion device to generate an alternating current (AC) heating current using the measured current, and apply the AC heating current to the battery system to heat the battery system to a desired temperature.