Investigation on Hybrid Cooling Topologies of Li-Ion Battery Pack for Electric Vehicles

The performance standards of Li-ion batteries used in EVs have skyrocketed, owing to their rapid commercialization in recent years. This has made Li-ion battery thermal management more vital than ever before, as optimum performance is achieved only when the batteries are within the narrow temperature range of 25° to 40°C. However, the operating temperatures in a lot of EVs go way beyond 40°C, leading to a reduction in the battery performance and lifetime. This study aims to solve this problem by improving the battery packing and maintaining the battery temperature via a hybrid cooling system which involves both air-cooling and liquid cooling. The aim is achieved by varying the liquid coolant used in the system and the cell arrangement in the battery module which has 32 cells in an 8x4 arrangement. Water-ethylene glycol solution and two other nanofluids, namely cu-nanofluid (1% vol) and CNT-nanofluid (0.1% vol) have been used as the coolants while the cell arrangements considered are the aligned, staggered and cross arrangements. In the numerical model of the 6Ah, 123 V battery pack, each battery cell generates about 5 W and is represented as a cylinder enclosed in a case with an air-cooling setup and two liquid cool plates on the top and bottom being directly in contact with the battery cells. The model is simulated using ANSYS Fluent for various cell arrangements and coolants to identify the temperature profile of the entire battery. The best cooling effect was achieved with the staggered configuration, with the liquid coolant being Cu-nanofluid (1%). In this case, the maximum battery temperature was limited to 35.078°C.