Experimental investigation of an alternative battery pack thermal management system

Abstract

Placing the batteries in PCM (Phase Change Material) filled containers causes a thermal imbalance in the pack because the heat can be dissipated from the sides, but it is accumulated in the center. An alternative geometry is proposed and tested to solve this problem. The thermal performance of the proposed battery pack structure employing PCM has been experimentally studied in free convection conditions. The battery pack is formed by placing 12 test batteries in the same size of 26650 LiFePO4 in custom-designed aluminum (Al 6065) chamber. The single-piece chamber consists of three subchambers connected by straight, rectangular, and parallel fins. The cells are positioned in the 4S3P arrangement. Three different PCMs with different melting temperatures are utilized, and their effect on the battery pack temperature is sought under a stagnant air environment (21 °C). The pack has been tested during discharging at 2C (1.3 W), 3C (2.75 W), and 5C (7.83 W). The heat generation values are adopted from the literature. The maximum temperature in the cells and the maximum temperature deviation between the cells are monitored while the cells are being charged or discharged for different test procedures. Instead of placing PCM and cells in a single case like in studies in the literature, a tailor-made finned geometry helped provide a more homogenous temperature in the cells thanks to the finned structure on the air side. In this way, the maximum temperature difference inside the battery pack is kept below 5 °C for all cases except the extreme case of cyclic 5C discharge/charge analysis with CrodaTherm47. The maximum temperature of the battery pack could be kept below the critical value (60 °C) only when CrodaTherm37 was employed for three consecutive cycles at a discharge rate of 5C/7.83 W as the fin temperatures could be kept at the optimum level, and the PCMs latent heat can be exploited the most.