THERMAL MANAGEMENT OPTIMIZATION OF LITHIUM-ION BATTERY PACKS FOR ELECTRIC VEHICLES

Abstract

Effective thermal management is essential to ensure the safety, performance and battery life of EVs, given the high rate of charging and challenging driving conditions in electric vehicles. This paper explores and contrasts four distinct thermal-management strategies for batteries: natural-air cooling, forced-air cooling, liquid-cold-plate cooling and a hybrid of the phase-change-material and liquid-cooled approaches. The following performance tests were conducted on each configuration: thermal performance (maximum cell temperature), temperature uniformity, thermal resistance, auxiliary power consumption, and expected capacity retention. The results showed that the overall thermal performance of the cooling configuration with a combination of both cooling methods was the best. Under 3C fast-charging condition, the hybrid system lowered the peak cell temperature to 36.8 °C, compared to 39.4 °C, 46.2 °C, and 52.8 °C for the liquid cold-plate cooling, forced-air cooling and natural convection systems, respectively. It also reduced the maximum temperature difference between the cells in the battery module to 2.1°C, showing greater temperature uniformity across the battery module. The hybrid system could maintain the temperature at an acceptable level in sensitivity analysis under the high ambient temperature and high charge rate condition. The coolant flow rate of 2.0 L min⁻¹ was optimised to give an appropriate balance between cooling effect and pumping power. Likewise, a 30% phase-change-material fraction resulted in significant thermal improvement with moderate module mass. Another battery ageing analysis also demonstrated that the hybrid system retained approximately 96.2% of the initial capacity at 800 accelerated cycles. The findings demonstrate that the proposed hybrid thermal-management system could improve the battery safety, energy efficiency, temperature uniformity, and battery service life, suggesting that it is a potential solution for high-performance electric-vehicle battery packs.