Hybrid thermal management of Li-ion battery pack: An experimental study with eutectic PCM-embedded heat transfer fluid

Abstract

Lithium-ion (Li-ion) batteries are widely used in the automobile, electronics, and aerospace industries due to their low self-discharge rate, extended lifespan, high efficiency, high power density, and superior operational performance. However, under extreme operating conditions, Li-ion batteries generate significant heat, which degrades their performance and can lead to thermal runaway. An appropriate cooling system is essential to improve battery life, safety, capacity, and performance. This study investigates the effects of various cooling methods on a 5000 mAh Li-ion battery pack during charging and discharging at 1C, 1.5C, and 2C rates. The cooling techniques evaluated are natural cooling, heat transfer fluid cooling, eutectic PCM cooling, and hybrid cooling. The eutectic PCM comprises lauric acid and stearic acid, with a melting temperature of 33.29 °C, a latent heat of 151.76 J/g, and a thermal conductivity of 0.356 W/mK. Experimental results indicate that with natural air cooling, the battery pack reaches maximum temperatures of 66.9 °C, 57.9 °C, and 45.6 °C when charging and discharging at 2C, 1.5C, and 1C rates, respectively. Compared to natural air cooling at the 2C rate, heat transfer fluid cooling reduced the maximum temperature by 22.42 %, eutectic PCM cooling by 40.90 %, and hybrid cooling by 46.18 %. These findings demonstrate that hybrid cooling significantly reduces both the maximum surface temperature and the temperature gradient, suggesting it as an effective method for cooling battery packs.