A Compact Resonant Switched-Capacitor Heater for Lithium-Ion Battery Self-Heating at Low Temperatures

Lithium-ion (Li-ion) batteries endure substantial energy loss and power recession under cold environments, requiring to be heated before starting normal operations in electric vehicles (EVs). Currently, many internal ac heating approaches powered by batteries have been proposed to achieve a fast heating speed, high efficiency, and good uniformity. However, due to the bulky size, high cost, and low ac heating frequency, the existing ac heating devices are generally improper for EV applications. In the light of this, a compact high-frequency heater is proposed in this article to achieve effective self-heating for Li-ion batteries. Specifically, based upon the resonant switched capacitors (RSCs), this heater is only powered by the on-board battery pack, leading to an easy implementation. Detailed analytical expressions of the heating current and efficiency are deduced and validated through various experiments. Illustrative results demonstrate that the proposed RSC heater is capable of effectively realizing battery self-heating without using external devices. Particularly, a reliable tradeoff between the fast heating speed (2.67 degrees C/min) and high efficiency (96.4%) is obtained by using two or more parallel-connected heaters. Due to the compact size, low price, high efficiency, and good reliability, the proposed heater can be also extended to preheat batteries of unmanned aerial vehicles, robots, phones, etc.