Effectiveness of Nail Penetration for Thermal Propagation Test in Battery Packs and Vehicles

The number of electric vehicles (EVs) has increased significantly in recent years. Consequently, incidents of EV fires have been reported. To protect passengers and evaluate battery robustness, thermal propagation tests are conducted. Typically, these tests initiate a cell in a battery pack using either a heater or a nail. While the heater method is commonly used, the nail method faces restrictions when selecting an initiation cell, especially for battery pack and vehicle testing. For battery pack testing, vertical penetration against the vehicle's travel direction does not have cell selection restrictions. However, for horizontal penetration, the initiation cells are limited to the outermost cells in the battery pack. In vehicle testing, horizontal penetration is unfeasible, whereas vertical penetration from bottom to top is possible. To demonstrate the feasibility of the nail method for battery pack and vehicle testing, especially in vehicles, nail tests were conducted on an electric vehicle battery pack and an electric vehicle equipped with the same battery pack. Additionally, gas measurements were taken during the tests. The results indicate that the nail test method is feasible for both battery packs and vehicles, as a single-cell thermal runaway was successfully initiated in both scenarios.