Presented by: Kelly Opert

UL is involved with the aviation industry to better understand the hazards from rechargeable batteries and identify potential mitigation solutions. Currently, rechargeable batteries primarily include Li-ion batteries either for bulk transportation or in electronic cargo (e.g., laptops, power banks, mobility devices). Incidents in passenger and cargo planes have highlighted the hazards to passengers and cargo planes from electronic devices with Li-ion batteries.

There is interest with the cargo carriers to develop an active fire suppression system for cargo containers to protect the plane and crew in an event of a fire involving electronic items or bulk transportation of li-ion cells.

Standardized test methods to evaluate the emerging technologies will require development of an ignition source that is representative of the hazard carried on aircraft. Research is required to identify a battery pack representative of a shipped item as it is the primary fire hazard that may initiate a fire event. Additionally, research is required to develop a standard fuel load that represents the shipped cargo.

The review of literature identified three areas for further investigation for identifying a representative ignition source in shipped cargo:

• (i)Influence of state of charge with a range representing limiting values considered by regulatory groups;
• (ii)Influence of electrical configuration and capacity of battery packs representing personal electronic devices, and appliances (e.g., e-mobility, hand tools, and garden tools) likely to be shipped as cargo.
• (iii)Influence of how cells are electrically configured in a battery pack.

The data showed that the state of charge of cells and battery packs increased the peak fire size as the state of charge increased. Even cells and battery packs at a “safe” state of charge consistently resulted in flaming combustion.

Multipacks (packs of not electrically connected cells) and battery packs were evaluated. It was found that the feature that drove the highest heat release rate was the shape of the pack rather than the electrical connections.

Another hazard to emerge from the data was the time between the first cell going into thermal runaway to the last cell burning out. This is critical because localized aviation suppression methods have a limited discharge duration due to convenience and cost. A delayed reignition after a suppression system has been fully discharged could render a suppression system ineffective.