An Integrated Heating–Charging Method for Lithium-Ion Batteries at Low Temperature

Aiming at the issues of low available capacity and difficult charging of lithium-ion batteries (LIBs) at low-temperature, existing low-temperature charging methods are difficult to achieve fast charging due to the splitting of the fast preheating and charging processes. Therefore, an integrated heating–charging method is proposed. Specifically, a compact integrated heating–charging topology (IHCT) based on bidirectional buck-boost converter is applied to connect the charger to the battery pack. The IHCT operating modes, including battery self-heating, charging, and simultaneous heating–charging (SHC), are varied by controlling the complementary PWM parameters. Further, the working principle of the IHCT is analyzed, and the influence laws of PWM parameters on the heating and charging performance are revealed, based on which a closed-loop SHC protocol and control framework is proposed. The experimental results demonstrate the validity of battery rapid self-heating under different scenarios. The proposed SHC framework can charge the battery from 20% to 80% SOC in 39 min at −20 °C without battery degradation observed. Compared with the direct charging and preheating–charging methods, the charging speed is improved by six and two times, respectively. The proposed method can not only provide flexible and fast heating for LIBs but also effectively reduce the low-temperature charging time.