Full-scene battery self-heating method based on powertrain system for electric vehicles at extremely low temperatures

Abstract

The popularity of electric vehicles (EVs) in the cold regions is seriously hindered by the degradation of lithium-ion batteries (LIBs) at low temperatures. To settle such issue, it is necessary to preheat the LIBs to moderate temperature for normal operation. As one of attractive internal preheating methods, pulse self-heating possesses high heating rate and efficiency. However, the application of pulse self-heating still faces the challenges of the pulse current power source unavailable in EVs. Herein we proposed a novel battery self-heating method which reuses the powertrain system of EVs to generate pulse excitation onboard, eliminating additional hardware. Moreover, the decoupled control of battery self-heating and motor torque was further developed to achieve the full-scene application, including charging, parking and driving. When applied in EVs, the proposed self-heating method could realize fast temperature rising of battery pack, shortening 30.7 % charging time at −20 °C compared with the conventional heat pump method. It also achieves rapid startup of EVs even at low temperature of −38 °C with high heating rate (0.73 °C min⁻¹) and low energy consumption (4.2 % SOC), as well as maintains the dynamic performance during driving at −30 °C. The proposed method provides a promising solution to preheat the battery pack for EVs application at extremely low temperatures.