Performance analysis of liquid-based battery thermal management system for Electric Vehicles during discharge under drive cycles

Abstract

The performance of an Electric Vehicle (EV) is determined by the battery pack's specific power, specific energy, self-discharging rate, and cycle life. However, these parameters are sensitive to temperature. Therefore, thermal management is the most critical factor defining a battery pack's performance in an EV. Even though thermal management of lithium-ion batteries has received a lot of attention, there has been minimal research on the performance of liquid based battery thermal management systems for Electric Vehicles for the actual drive cycles like the Indian drive Cycle and Federal Test Procedure (FTP-75) drive cycle. This study investigates the thermal behaviour of the Li-ion battery pack of an EV and the performance of a liquid-based battery thermal management system with various coolant options, such as Water, Water-Ethylene Glycol mixture, and Water-Propylene glycol mixture for both Indian Drive Cycle and FTP-75 (Federal Test Procedure) Drive Cycle. The numerical simulation is carried out for a battery pack with four modules, and liquid-based battery thermal management is designed at the pack level, considering the heat generated in the battery pack. The variation of battery pack temperature and cumulative energy consumption by the battery thermal management system (BTMS) is also investigated. The simulation model is designed in such a way that it tries to maintain a set battery pack temperature of 25 °C. Also, the effect of ambient temperature on the performance of the liquid cooling system has been analyzed. The results indicated that with the increase in ambient temperature the BTMS takes a longer time to cool the battery pack and cumulative energy consumption by the liquid based BTMS also increases for both the drive cycles. In the case of Water-Propylene glycol mixture, 25 % propylene glycol concentration is recommended, whereas in the case of Water-Ethylene glycol mixture, 50 % ethylene glycol concentration provides the best performance as both cumulative energy consumption by the battery thermal management system and temperature distribution in the battery pack are optimum.