Experimental analysis of the influence of ambient temperature for a Loop Heat Pipe based Battery Thermal Management System

In Battery Thermal Management System (BTMS), Loop Heat Pipes (LHPs) may act as thermal vectors connecting the bottom of the battery pack with the remote chiller of the EV's HVAC system, whilst graphite sheets allow to achieve satisfactory temperature homogenization of the cell surface, containing the added system weight and thermally isolating one cell to the other. This design was developed aiming to improve on fast charge timings, all-electric range and to reduce costs and complexity. Preliminary studies revealed the potential of this innovative passive BTMS for providing better performance than an active BTMS using a liquid cold plate. Taking a further step in the direction of practical applications, the present work investigates how the proposed innovative BTMS performs in different ambient temperatures by showing the results of several fast charge and heating tests inside an environmental thermal chamber, with temperatures ranging between −20 and 50 °C. The results show that the considered LHP worked in all the tested conditions, and that the heating delay brought by the LHP during heating phase (i.e., final temperature 1.2 °C lower than without the LHP) was surpassed by the temperature reduction during the cooling phases (i.e., 3.2 °C temperature reduction at high temperatures).