High-Efficiency Resonant Push-Pull AC Heater for Lithium-Ion Battery Pre-heating at Low Temperature

Lithium-ion batteries suffer from serious problems in charging and discharging in a low-temperature environment, and battery pre-heating methods are being actively conducted to solve this problem. The internal heating method which uses the ohmic loss of the battery internal resistance can be implemented with an on-board self-heater without an external power source, and is suitable for electric vehicles or portable devices. This paper proposes a new resonant push-pull AC heater. The proposed heater reduces voltage stress and switching loss by connecting a resonant capacitor to the switch in parallel. In addition, it has a small volume as it can achieve ’all-time heating’ of a battery without an interleaving structure. In order to verify the effectiveness of the proposed AC heater, an experiment was performed to preheat a lithium-ion battery of 8 series-2 parallel 18650 type from −20°C to 0°C.