Experimental Investigation of Integrated Heat Pipe—Liquid Cooling for a Battery Pack

This study investigates a hybrid tab-cooled heat sink combining sintered-wick copper heat pipes embedded in a high-conductivity aluminum block with computer numerical control machined serpentine liquid cooling channels for a 15-cell lithium-ion battery pack (capacity: 2.5 Ah per cell, parallel connection). Performance was evaluated under constant-current discharge rates (1, 3, and 4 C, where C denotes nominal capacity rating) and automotive drive cycles (Urban Dynamometer Driving Schedule (UDDS), Short Dynamometer Driving Schedule (SDDS), and Worldwide Harmonized Light Vehicles Test Procedure) at coolant flow rates from 0 to 0.5 liters per minute. At 3 C discharge, peak temperature decreased from 81.6 °C to 62.9 °C with active cooling, extending safe operation from 50 to 93% depth-of-discharge before reaching the 60 °C threshold. Temperature variation among cells was reduced by 40%. Dynamic drive cycles showed peak temperature reductions of 19 °C (UDDS) and 22 °C (SDDS). Thermal resistance analysis revealed maximum reductions of 66% (1 C) and 39% (3 C) versus baseline. At low discharge rates, the system is convection-limited, making liquid cooling highly effective. However, at high rates (3–4 C), heat pipe operational limits become the primary constraint, indicating applications requiring sustained operation above 3 C would benefit more from enhanced heat pipe capacity than from increased liquid cooling flow rates.