Performance Characteristics of a Composite Battery Thermal Management System Combining Heat Pipes and a Cooling Plate

To improve the efficiency and safety of lithium-ion battery (LIB) systems, an effective battery thermal management system (BTMS) is required to keep the batteries at the optimal operating temperature and the minimum temperature difference. In this study, a novel BTMS integrating heat pipes and cooling plates was designed, and its performance was investigated experimentally and numerically. Firstly, the cooling performance of different types of BTMSs was compared. Moreover, the effects of the composite BTMS were investigated at different discharge rates and flow rates. Finally, the preheating performance of BTMS at different ambient temperatures was examined. The results showed that the peak of the maximum temperature (Tmax) reached 74.4 ℃ in charge-discharge cycles at natural convection. The liquid cooling could mitigate the temperature elevation during high-rate discharging, but there was still a large temperature difference in the battery pack (more than 8 ℃). In the composite BTMS, the addition of heat pipes helped to meet the requirements of keeping Tmax and the maximum temperature difference (ΔTmax) at different discharge rates. However, the performance of the BTMS was difficult to be further improved by increasing the flow rate (Qflow) but resulted in an increase in ΔTmax. For preheating at low temperature by BTMS, it took only 200 s to heat the battery from -20 ℃ to -10 ℃ to ensure the battery discharge capacity at a low rate, and the time required to heat the battery to 0 ℃ that meets the requirement of high-rate discharge was less than 610 s.