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

<div class="section abstract"><div class="htmlview paragraph">The number of electric vehicles (EVs) has significantly increased in recent years. Safety performance of EVs is at least at the same level as that of conventional vehicles. To evaluate battery safety and ensure passenger protection, several standard tests and regulations for EV batteries have been established, including IEC 62660-3, ISO 6469-1, and UN/ECE/R100 Revision 3. ISO 6469-1:2019/Amd 1 specifies thermal propagation (TP) test to evaluate battery robustness against thermal runaway (TR) in a single cell. Moreover, UN/ECE/R100 Revision 3 aims to provide sufficient egress time to protect passengers in the event of a TR in a single cell.</div><div class="htmlview paragraph">Typically, these tests initiate TR in a cell within a battery pack using either a heater or nail. In the heater method, if the gap between cells is larger than the heater’s thickness and there are no installation constraints due to components, almost any cell can be chosen as the initiating cell. However, if the gap between cells is smaller than the heater’s thickness, the initiating cell is limited to the cells at the edge of the module. On the other hand, the nail method faces restrictions, especially for battery packs and vehicle testing. For battery pack testing, vertical penetration against the vehicle travel direction imposes no cell selection restrictions. However, for horizontal penetration, the initiation cells are confined to the outermost cells of the battery pack. In vehicle testing, horizontal penetration is impractical, whereas vertical penetration from bottom to top is feasible.</div><div class="htmlview paragraph">To demonstrate the feasibility of the nail method for battery pack and vehicle testing, nail tests were conducted on an electric vehicle battery pack and an electric vehicle equipped with the same battery pack. Gas measurements were performed during the tests. The results indicate that the nail test method is feasible for both battery packs and vehicles because single-cell TR was successfully initiated in both scenarios. This demonstrates the potential of the nail method for comprehensive TP test of EVs.</div></div>