Abstract: Fire tests on EVs were carried out to measure the heat release rate and total heat release of the EV fires to provide technical support for comprehensive understanding of the fire hazards of electric vehicles, the rational determination of fire fighting and rescuing strategies and prevention and protection measures for electric vehicles and car parks. The influence of different factors on the heat release rate of electric vehicle fires is also presented in this paper. The research results show that the fire growth rate induced by over-charging batteries to ignite the EVs is significantly larger than other ignition methods like over-heating batteries and external fire sources. The development of the heat release rate curve of inducing a NCM lithium battery by over-heating to ignite the vehicle is similar to that of inducing a lithium iron phosphate battery by over-charging to ignite the vehicle. When an external fire source of about 300 kW was used underneath the carriage to ignite the EV, the fire growth rate was approximately equivalent to that of a medium-speed fire. When an external fire source of about 30 kW was used underneath the carriage to ignite the EV or a fire source of 5 kW was used to ignite the interior of the EV carriage, the fire growth rates were approximately equivalent to that of a slow-speed fire. For the electric vehicles of the same model, the maximum heat release rate caused by thermal runaway of the lithium battery was higher than that caused by an external fire source. However, the total heat released during the tests were identically the same despite the different ignition method.

Key words: electric vehicle, lithium-ion battery, thermal runaway, fire spread, fire heat release rate