In recent years, environmental regulations such as the reduction of greenhouse gas emissions have been attracting significant attention around the world. Therefore, demand for battery electric vehicles (BEV) that emit no greenhouse gas while driving is expected to increase in near future. Lithium-ion batteries, which are the power source of BEV, are required to be precisely thermo-controlled at narrow temperature range, because at high temperature environment, the aging is advanced, meanwhile at low temperature environment, the driving range is shortened by the increase in the internal resistance of the battery cell. Therefore, it is important to optimally design the cooling passage inside the battery pack and the battery cooling structure that keep the battery temperature at an appropriate range with minimum temperature difference between cells. The cooling structure, consisting of battery modules, cooling plates and thermal pads, requires both of the cooling performance and the structure durability under various driving conditions. The purpose of this study is to develop the battery cooling structure and the passage inside the battery pack that highly balance high cooling performance and sufficient structural durablity with light weight. The flow path shape in the cooling plate was optimally determined by combination of computational fluid dynamics (CFD) and optimization tool so that the required thermal transfer rate was fulfilled under minimum pressure loss across the flow path. In addition, the cooling water inlet diameter of each cooling plate connected in parallel was optimized to minimize the flow rate variation between the cooling plates, which enables the reduction of cell temperature variation. And using structural analysis, we worked on optimizing the cooling plate and mount stiffness in consideration of the characteristics of the rubber mounts and thermal pads, which are essential for the floating structure. As a result, the cooling plate holding structure was designed to ensure the durablity under various driving conditions. Moreover, we succeeded in developing a cooling structure that secured the contact between the battery modules and thermal pads for each vibration input. The results not only achieved high cooling performance and sufficient structural duablity, but also contributed to the reduction in parts number for the structure. The developed cooling structure was adopted into “Honda e” released in 2020.

Mr. Noriyasu Hakuta, Honda R&D Co.,ltd. Automobile Center Tochigi, JAPAN Mr. Yosuke Yamagishi, Honda R&D Co.,ltd. Automobile Center Tochigi, JAPAN Mr. Manabu Matsumoto, Honda R&D Co.,ltd. Automobile Center Tochigi, JAPAN Mr. Katsuya Minami, Honda R&D Co.,ltd. Automobile Center Tochigi, JAPAN Mr. Kaito Shinoda, Honda R&D Co.,ltd. Automobile Center Tochigi, JAPAN