This conference paper was submitted for presentation at the NAFEMS World Congress 2025, held in Salzburg, Austria from May 19–22, 2025.

Abstract

In the event of significant structural or thermal abuse to a battery cell, elevated temperatures can trigger a runaway exothermic reaction that can propagate throughout the pack. During thermal runaway, the pressure relief mechanisms of the pack will result in venting (degassing) of hot, combustible gases. The potential for high temperatures and fire poses a significant danger to vehicle occupants and first responders. For this reason, regulations to guarantee 5 minutes for occupant egress before a hazardous situation in the vehicle cabin have been implemented in China, with similar regulations anticipated globally. To meet these global safety standards, OEMs must investigate the integration of runaway propagation prevention and damage mitigation methods within battery pack and vehicle designs. This paper presents a transient simulation workflow that is capable of simulating thermal runaway propagation of multiple cells inside the battery pack for a duration of up to 30 minutes and the effect on the external vehicle system components due to the degassing. The method is a coupled approach between a 3D CFD solver that simulates the convection and a 3D thermal simulation software that handles the conduction and radiation. By coupling and decoupling the convection from CFD and the conduction/radiation solver, long transient scenarios can be simulated with quick turn-around times without compromising on accuracy. The simulation includes a predictive method for determining when the next battery cell goes into thermal runaway, which will then automatically cause the cell temperature increase and venting. It will be demonstrated how this workflow can be applied to vehicle thermal analysis and heat protection studies, how to slow down the propagation of thermal runaway or even completely prohibit it by applying thermal insulation materials between the cells. Surrounding components can be protected by applying shielding, to avoid these components to melt or catch fire. The cabin compartment floor and carpet temperatures can be predicted, and insulation materials can be applied to avoid the temperatures inside the cabin to get too high or to catch fire, potentially endangering vehicle occupants.