COMPARISON BETWEEN DIFFERENT BATTERY THERMAL MANAGEMENT SYSTEMS DURING FAST CHARGE CYCLES

Aiming to improve on fast charge timings, all-electric range and to reduce costs and complexity, a Battery Thermal Management System (BTMS) with Loop Heat Pipes (LHPs) and graphite sheets is proposed. The LHP placed at the bottom of a prismatic cell module will transfer heat from the cells to a chiller, already part of the HVAC system of the vehicle (hence reducing complexity). Graphite, due its woven structure, provides excellent heat transfer in one direction, and insulation from cell to cell. LHPs do not need pumps or moving parts, nor they need additional energy sources to transfer heat, contrarily to an active forced convection system using fans or pumps. This work investigates the performance between the passive BTMS proposed by the Authors, another passive cooling method (free convection) and an active BTMS (liquid cold plate), thanks to a previously validated code. It resulted that free convection, compared to the LHP-based and cold plate BTMS, can contain maximum cell temperature at low values of C-rates, but is not able to reduce the temperature once the vehicle returns to normal driving conditions. Furthermore, results showed potential for the LHP BTMS to contain the cell temperature below 50°C at 5C fast charge conditions (7 minutes) and to reduce the maximum cell temperature by 7.9ºC compared to free convection and even by 2ºC compared to the active liquid cold plate.