High-Frequency AC Heating Strategy of Electric Vehicle Power Battery Pack in Low-Temperature Environment.

In this paper, a heating strategy using high-frequency alternating current (AC) is proposed to internally heat lithium-ion batteries (LIB) at low temperatures. The strategy aims to strike a good balance between rapid heating of the battery at low temperatures and minimizing damage to the battery's lifespan without the need for an additional power source. The strategy presents an electrochemical-thermal coupling model to simulate and predict the temperature rise and temperature distribution of a 50 A h LiFePO square battery at different C-rates, the effect of high-frequency AC on battery life, and the validity of the model as verified by experiments. The experimental and simulation results show that this strategy can achieve faster heating speeds and better temperature consistency without affecting battery life. The best heating effect can be achieved at a frequency of 500 Hz (4.2C), and the temperature of the battery rises from 253.15 to 278.15 K within 365 s, for an average heating rate of 3.29 K/min. Researching low-temperature AC heating methods has important value for energy conservation because it can improve heating efficiency, expand application areas, promote technological innovation, and enhance product quality.