Thermal mapping analysis of a 48V prismatic lithium-ion battery pack with active and passive cooling

Abstract

This experimental study investigates the thermal behavior of a 48V lithium-ion battery (LIB) pack comprising three identical modules, each containing 12 prismatic LIB cells, during five charge-discharge cycles. A homogeneous liquid cooling system is applied at the bottom of the modules to control the pack temperature when it reaches 40°C (active cooling phase). The initial two cycles represent passive cooling, where the cooling liquid remains stationary. Temperature distribution is measured and analyzed using 27 thermocouples, providing insights into temperature changes in the cells, modules, pack, and cooling system inlet/outlet. Results show that in passive cooling cycles, minimum temperature occurs at pack surfaces due to better convective heat transfer, while maximum temperature is observed in the central LIB cells. The active cooling phase alters the temperature distribution within the pack. One module is found to be more sensitive to high currents, generating more heat and releasing it faster. Additionally, the positive tab temperature is higher than the negative tab temperature within a single cell. The liquid cooling system decreases the temperature rise from 5.8°C to 3.5°C in the discharge cycles with a constant current of -237A. This study emphasizes the significance of evaluating the thermal behavior of individual modules and highlights the complexity of the LIB pack system, as well as the impact of an indirect liquid cooling system on enhancing its thermal performance.