A composite of a phase change material and aluminum sheets has been used for the thermal management system of LiFePO₄ pack to control the temperature rise of the batteries at high temperature regions (50-55 ^oC). Poly Ethylene Glycol 1000 (PEG1000) with melting point of 35-40 ^oC has been selected as a phase change material. Aluminum sheets have been applied to the PCM for thermal conductivity enhancement and also to improve the temperature uniformity of the system. Preliminary experimental runs have been performed in charge and discharge of the batteries at different rates of 1C to 3C to obtain the maximum surface temperature of the batteries. A mathematical model has been developed in COMSOL ver. 5.1 and the results of the model have been verified by the experimental data obtained at different conditions. The experimental data has been compared The results show that using the PCM and aluminum sheets between the cells can reduce the surface temperature significantly and causes better performance and temperature uniformity of the battery pack. The maximum cells surface temperatures at ambient temperature condition have been reduced by 19%, 21%, and 26% for the rates of 1C, 2C, and 3C respectively.