Inclined battery cells for mitigating damage in undercarriage collision

Abstract

Undercarriage collision is dangerous for electric vehicle as battery pack is usually integrated into the vehicle floor. If battery pack is ploughed by obstacle on road, battery cells could be damaged, increasing risk of occurrence of internal short circuit and thermal runaway. To tackle the problem, we came up with inclined layout of battery cells for reducing damage in undercarriage collision. Using numerical simulations, we show why inclined battery cells can alleviate damage in undercarriage collisions. The load cases include vehicle’s initial speeds from 20 to 100 km/h and battery pack clearance overlapped with obstacle from 10 to 30 mm. Aligned with the new cell-to-pack packaging trend, the battery pack model used in this study only includes large size battery cells and has no module-level assemblies. A homogenised model of deformable battery cell was adopted for assessing damage. The results have shown that forward inclination of battery cells can reduce scraping resistance to battery pack, and thus lower the impact energy transferred to battery cells and jellyrolls. The 20° forward inclination was found to deliver better safety performance than the other layouts. Optimal inclination angle depends on structural design of battery pack and battery cells. In general, the safety enhancement is more prominent in severer undercarriage collisions.