Lithium-ion battery preheating strategy based on on-board inverter and motor

Lithium-ion power batteries are the main source of energy for electric vehicles (EVs). However, they suffer from performance degradation and capacity loss in low temperature. And there are safety hazards in charging lithium-ion batteries directly in low-temperature environments. Therefore, a preheat strategy must be adopted to heat the lithium-ion power batteries before charging. In this paper, an internal preheating strategy is presented. The on-board inverter and the three-phase permanent magnet synchronous motor of the EVs are used to form a current path. When current passes through the battery, the internal resistance of the battery is used to generate heat to achieve the purpose of heating. Based on the original drive circuits on electric vehicles, the battery is divided into two groups, where the connection between the battery groups and the inverter is changed, and an improved topology is researched. A simulation model including inverter module, SVPWM control module, three-phase permanent magnet synchronous motor module, and current control module is established. Through simulation analysis, it is verified that the improved topology can obtain a larger heating current on the battery. Then, the experimental setup is built to verify the effectiveness of the preheating strategy. A group of experiments take 18650 type lithium-ion phosphate power batteries as the research object are conducted, achieving a battery temperature rise of 0.55 °C per minute It is verified that the preheating strategy will not cause significant damage to the capacity of the battery, feasible and promising in EVs.