February 5, 2024
E-mobility has the potential to play a crucial role in the decarbonization of urban environments. There are more e-bikes and e-scooters today than ever before, and the vast majority of them use high-energy lithium-ion battery packs. Fire incidents involving these battery packs are rare, but such fires do happen, and the consequences can be serious. In 2022 alone, the New York City Fire Department responded to 200 e-scooter and e-bike fires, and in 2023, London saw a record high number of similar fire incidents.
In a newly published paper titled "Evaluation of Fire Spread and Suppression Techniques in Micro-Mobility Battery Packs," Exponent's Daniel Torelli, Nicholas Faenza, Sam Lawton, and James Frake, with coauthor Phil Johns, detail the results of experiments they performed to extinguish lithium-ion battery fires. The team tested various fire suppression methods commonly available in the average household on lithium-ion battery packs experiencing thermal runaway events and subsequent fires. For example, their results demonstrated that dousing batteries in moderate amounts of water slowed propagation of thermal runaway but wasn't enough to extinguish it, and that fire blankets failed to contain the thermal event, smother the fire, or contain ejecta.
In addition to extinguishing methods, the authors explore how various battery pack designs can help limit cell-to-cell propagation and reduce the severity of a single cell failure, including the potential of certain insulating materials to greatly reduce the amount of damage to a battery pack during a thermal runaway event.
From the publication: "The water hose was unable to supply a sufficient amount of water to extinguish the thermal event, however, the average pack temperature was decreased and the cell-to-cell propagation rate was slowed. Neither fire blanket tested was able to contain the flames or debris ejected from the battery packs and both acted to hold in the heat from the event … "