Abstract: Based on the ISO 9705 fire standard experiment, the thermal runaway of 48 V/20 Ah soft pack battery module was triggered by overcharging, and the voltage and surface temperature of the battery pack, the rate of heat release, the total amount of heat release and the flame temperature of the e-bike were measured and analysed. The results show that: the maximum surface temperature of the battery surface rises to 816.28 ℃, and the voltage of the battery plummets to nearly 0 V in about 600 s; the fire triggered by overcharging of the e-bike presents the form of spreading from the top to the bottom, and the maximum flame temperature is 848.8 ℃; the maximum heat release rate is 4 858.89 kW, and the total heat release amount is 1 219.03 MJ; The maximum heat release rate of the battery pack is about 4.54% of the maximum heat release rate of the whole vehicle, and the total heat release is about 8.40% of the total heat release of the whole vehicle, and the plastic, sponge and leather of the e-bike contribute a significant heat release rate (about 90%). The results of this study emphasize that e-bike fires are composite fires, and provide an important reference for the timing of extinguishing e-bike fires.

Key words: lithium iron phosphate battery, thermal runaway, electric bicycle, combustion behaviour, heat release rate