An Integrated Bidirectional Pulse Current Self-Heating System for EV Battery With an Optimized Heating Strategy

To address severe capacity degradation and power deterioration of lithium-ion cells in low-temperature environments, this study proposes a Bidirectional Pulse Current Self-Heating (BPCSH) system. The system forms a preheating circuit by integrating the on-board EV motor stator windings, the inverter's three-phase bridge arms, and the battery pack. This configuration enhances the preheating current rate through three phase parallel operation, enabling rapid thermal conditioning of the battery pack. Furthermore, to mitigate terminal voltage over limit risks during high state-of-charge (SOC) operations under large currents, a resistor is employed to enhance the DC component of the preheating current. A static adjustment strategy is proposed to preset the resistance values before preheating, achieving optimal balance between rapid thermal response and energy efficiency while ensuring the battery terminal voltage within the safe limit, thereby achieving rapid temperature rise across full SOC ranges. Experimental results demonstrate heating rates of 4.52°C/min and 5.71°C/min (from 20°C to 0°C) under high and low SOC conditions, respectively, and 7.5°C/min for intermediate SOC scenarios. Notably, the cells exhibit negligible capacity degradation after 420 heating cycles. This work provides a cost-efficient and hardware-compatible solution for battery thermal management in low-temperature EV operations.