Experimental study of the suppressing effect of the primary fire and thermal runaway propagation for electric bicycle batteries using flood cooling

Abstract

With the continuous development of lithium-ion batteries (LIBs), electric bicycles have embarked on a trend of lead-acid batteries replacing with LIBs. However, thermal runaway (TR) during the charging process can trigger thermal runaway propagation (TRP) and fire issues, posing potential hazards in LIB applications. Therefore, effective tactics are urgently needed to prevent or mitigate these hazards. This study investigated the TRP characteristics of lithium manganese oxide (LMO), lithium iron phosphate (LFP), and nickel-cobalt-manganese (NCM) cathode-based batteries, which were utilized for electric bicycles. Furthermore, a novel charging cabinet with a flood cooling function was proposed to suppress primary fires and the TRP of electric bicycle batteries. Moreover, the mechanism of TRP suppression by flood cooling was quantitatively analyzed from the perspective of cooling power, heat transfer power, and self-heating generation power. Finally, the TRP characteristics and flood cooling effect of NCM battery-based packs were also studied. Results demonstrated the effectiveness of flood cooling on suppressing primary fires and TRP, which further addressed the issues of temperature rebound and reignition after battery extinguishment. Flood cooling effectively suppresses the TRP of LMO and LFP cathode-based batteries. However, it could not suppress the TRP of NCM cathode-based batteries. This study guides the battery selection and safety design of electric bicycles, and it is recommended to use LMO and LFP batteries.