Abstract:

Thermal runaway propagation (TRP) within a battery module, triggered by the thermal runaway of individual cells, is a significant cause of severe accidents in battery systems. To investigate the TRP behavior of real battery modules and their associated transportation risks in containers, this study focuses on 1P31S battery modules and conducts full-scale experiments simulating packaging transportation scenarios. The effect of the state of charge (SOC) on the TRP process is emphasized. The results indicate that simultaneously triggering two cells through heating does not initiate TRP in modules with 30% SOC but can cause thermal runaway in 9—10 cells in modules with 100% SOC (where four triggered cells are fully charged, and the remaining cells are at 30% SOC). The TRP speed ranges from 0.0315 to 0.0606 mm/s and leads to the melting of the packaging expanded polyethylene (EPE) foam and the plastic top cover of the module. As SOC increases, the maximum temperatures of the cells and packaging box, TRP speed, and heat transfer all increase. The maximum temperatures measured in the triggered cells and adjacent cells in the 100% SOC module were 495.2 ℃ and 649.5 ℃, respectively, significantly higher than 237.2 ℃ and 131.9 ℃ in the 30% SOC module. Furthermore, the substantial heat generated by TRP in the 100% SOC module caused the maximum temperature at the top center of the packaging box to reach 57.1 ℃, nearly double that of the 30% SOC module. Cells at 30% SOC did not fail when the heat received from the previous cell through thermal conduction was no more than 117.1 kJ but experienced thermal runaway when the received heat exceeded 140.8 kJ. In contrast, only 61.2 kJ of heat was required to trigger TRP among cells at 100% SOC. This study provides a reference for battery module design and the safety of battery module transportation in containers.

Key words: battery module, thermal runaway propagation, state of charge, temperature, heat transfer