Fire Hazards Associated with the Use of Water and Glycol as Coolants for Li-Ion Battery Systems

Abstract A few large fires in Lithium-ion battery systems are known to have been caused by leaking coolant, and experience from fire testing indicate that coolant can be the origin of violent fires triggered before the onset of thermal runaway in the battery. It is here hypothesized that the common coolants water and ethylene glycol can form flammable gases via electrolysis in the electrical environment found in battery modules and packs, and that electric breakdown can subsequently be triggered and result in formation of thermal plasma that further enhance evaporation and gas formation from the coolants. In this short communication, the potential hazards are analyzed with a basis in evidence from the literature, and in a theoretical perspective, as well as from anecdotal experience.