B. Kwon, C. Lopez, D. Overall, B. Connolly, V. Premnath and J. Jeevarajan
UL Research Institutes,
United States
Keywords: Li-ion battery, thermal runaway, fire suppression, aircraft cargo compartment
Summary:
The widespread use of portable electronic devices has substantially increased the number of Li-ion batteries carried in aircraft cabins and cargo compartments, leading to a growing number of fire incidents involving Li-ion batteries across the aviation industry. Despite the evolving risks, there is insufficient experimental data to validate the effectiveness of current aircraft fire suppression systems in mitigating Li-ion battery failures under in-flight conditions. This study aims to characterize thermal runaway of portable Li-ion battery products and explore the efficacy of suppressants against the resulting fires. Commercial laptops and mobility aid batteries were chosen as test articles in this study as these have been of major concern to the aviation industry in recent years. The batteries in these devices were thermally abused by installing a heating tape to one or more cells in the battery to initiate thermal runaway. The test article was located inside a chamber with an air exchange rate similar to that of an aircraft cargo compartment. Baseline tests were conducted during which no suppressants were engaged to understand the outcome when such test articles are thermally abused. Subsequently, tests with different suppressants that included water, water additives, and Halon 1301 were tested to evaluate their effectiveness. The suppression tests were conducted with the mobility aid battery serving as the test article. Results from baseline tests of laptops show that thermal runaway of the trigger cell was observed, however, propagation to adjacent cells was not observed and hence in some cases, multiple cells needed to be taken into thermal runaway. In the case of the mobility aid battery, full thermal runaway propagation was observed with a single trigger cell. From the results of the suppression tests, it was found that water and water additives successfully stopped thermal runaway propagation by lowering battery temperature, while Halon 1301 was unable to suppress the battery fire. The findings highlight the importance of assessing current aircraft fire suppression equipment against fires involving commercial Li-ion batteries and exploring alternatives to effectively mitigate the associated risks.