Full-scale experimental study on electric vehicle fire evolution and occupant cabin hazards induced by battery thermal runaway

The incidence of electric vehicle (EV) battery thermal runaway–induced fires has been increasing, posing severe risks to life and property. This study employed a large-scale calorimeter and a dedicated EV fire testing system to investigate full-vehicle fires triggered by battery thermal runaway. Key fire parameters, including heat release, flame behavior, and cabin smoke and temperature evolution, were analyzed. The experimental results showed that the EV fire lasted approximately 108 min, with a total heat release of 7.88 GJ. The HRR curve exhibited three distinct peaks. The first peak (3.363 MW) occurred during the initial ignition stage and was mainly attributed to jet flames generated by battery thermal runaway and the ignition of combustible components in the front compartment, with a medium fire growth coefficient of 0.0243 kW/s 2 . The second peak (4.159 MW) occurred during the intense combustion stage, contributing 40.1% of the total heat release, and was mainly associated with the combustion of occupant cabin materials. The third peak was related to battery pack reignition in the later stage. Cabin hazard analysis indicated that occupants were exposed to a severe smoke environment well before the battery pack deflagration occurred; smoke reached the dangerous threshold of 1000 ppm at 824 s after thermal runaway, earlier than CO (600 ppm) and SO 2 (100 ppm). Head temperature of occupants reached a lethal 120 °C at 1147 s. Maximum cabin temperature reached 993.1 °C, propagating from top to bottom and front to rear. These results elucidate the development mechanism of EV fires and the evolution of hazardous conditions in the occupant cabin, providing critical data for fire risk assessment and optimization of firefighting strategies.