The present study reports an experimental investigation carried out for the thermal management of cylindrical lithium-ion battery simulator using aluminium oxide (nano particle)-eicosane (phase change material) composites. The experiment involves varying the power input from 4 to 10 W in 2 W increments and adjusting the weight percentage of nanoparticles (wt %) from 0.5 to 0.9 in 0.2 wt % intervals. The examination of battery temperature evolutions in response to heating power, a comprehensive heat transfer analysis incorporating Nusselt number, determination of maximum temperature difference, thermal resistance analysis, and exploration of temperature variations in the absence of Phase Change Material (PCM) are considered. The results show that increase in weight percentage of alumina nanoparticles in phase change material cannot always improve the thermal performance. The results of the present study give a guideline for designing battery thermal management system. The power levels used in the experiment vary from 4 W to 10 W in steps of 2 W. For a power level of 4 W, the heat flux is 1.088 kW/m2, and for a power level of 10 W, the heat flux is 2.72 kW/m2.