Rule-Based Control of Battery External Heating for Electric Vehicle During Driving at Low Temperatures

Abstract

As the only power source of pure electric vehicles, lithium-ion batteries play an important role in vehicle powertrain systems. However, lithium-ion batteries have a significant reduction in capacity and power capability at low temperatures, which results in a greatly shortened driving range and poor acceleration of the vehicle. In this study, a rule-based battery external heating control strategy was developed to heat the battery during driving. An electrothermal film was affixed to the surface of each cell as an external heating material that was powered by the battery. An equivalent circuit model combined with a thermal model was established to simulate the electrical and thermal dynamics of the system with sufficiently high accuracy, and control rules were developed based on the model. The optimal solution was obtained by adopting the dynamic programming algorithm to optimize the trade-off between temperature rise and energy consumption and maximize the total driving range under different low temperature driving conditions. Simulation results on the experimentally validated model show that the vehicle with the proposed control algorithm increased the total driving range by 18.6% to 220% for different driving conditions at cold to extremely cold temperatures compared with the vehicle without external heating. Furthermore, the rule-based control showed a 1.1% to 4.4% improvement compared with the maximum (constant) power heating method.

Keywords

• Lithium-ion battery
• external heating
• electric vehicle
• driving range
• rule-based control
• dynamic programming