The UK’s Civil Aviation Authority (CAA) has commissioned University of Warwick to investigate how battery characteristics can affect thermal runaway risk, and complete a review of lithium-ion battery firefighting methods The report presents a consolidated proposal for rescue and fire fighting staff to tackle thermal runaway (TR) fires to eVTOL aircraft batteries.
“High charge and discharge rates, particularly relevant for the operational requirements of eVTOL, increase the likelihood and severity of TR,” said the report. “Once a cell is selected, the TR risk of an eVTOL aircraft battery pack/system largely depends on the design choices to mitigate cell TR propagation to neighbouring cells, and if propagation happens, containment. Current regulatory guidelines, i.e. RTCA DO-311A and EASA MOC VTOL.2440 emphasise stopping the cell TR propagation and containment of TR within the battery enclosure if cell TR propagates.
“Adhering strictly to these requirements, combined with regular monitoring and maintenance, is expected to minimise the probability of cell TR and its propagation. However, extreme scenarios resulting from conditions beyond the testing and certification envelope cannot be eliminated. Different abuse scenarios, such as a damaged battery enclosure and pack due to an uncontrolled landing, or fire originating from a non-battery component, may lead to an uncontained battery pack TR. In such a scenario, the Rescue and Fire Fighting Service (RFFS) personnel at an airport/vertiport need to respond and manage the incident.”
Traditional methods of firefighting at incidents involving gasoline powered vehicles do not apply to EVs, said the report. “There is no single method which can be applied for any EV battery thermal runaway; it depends on various factors. Current EV firefighting methods are effectively composed of two approaches: actively extinguishing the fire and managing the fire while allowing controlled burn. Immersion or flooding the battery packs with cooling media e.g. water to actively contain a TR event have been used. To avoid reignition and highly hazardous waste from the run-off, firefighters may consider using a controlled burn of the battery pack, while isolating the vehicle to prevent the fire from spreading to the surroundings. This approach has gained significant attention, as it offers the most efficient, quickest, and lowest impact on the environment. It also removes the reignition risk and less hazardous debris.”
For more information
https://www.caa.co.uk/our-work/publications/documents/content/cap3203/