Detection and Challenges in Early Detection of Thermal Runaway in Batteries
The possibility of thermal runaway in a lithium-ion battery makes battery electric vehicles (EV) a different fire risk compared to internal combustion engine vehicles (ICEV). One of the challenges is early detection of a thermal runaway. To identify potential techniques and challenges for detection of a thermal runaway, tests with batteries and detectors have been conducted and reveal several challenges.
While the number of battery electric vehicles in society is growing rapidly, batteries, and especially lithium-ion batteries, pose a different fire risk compared to traditional combustion engine vehicles. To improve the chances of successful firefighting, early detection has been put forward as desirable. In a recently finished study, detection techniques for early detection of thermal runaway in batteries were studied. Six different detection techniques were evaluated in this work.
Summary of the Tests
Different detectors, based on different techniques, were evaluated with thermal runaway in a single battery cell. The detectors were either of point-type (smoke and heat, LEL, or CO detectors) or based on camera techniques (thermal imaging, LIDAR, video analytics). Thermal runaway in the cell was triggered by external heating. The thermal runaway resulted in gas release without ignition. Different scenarios (e.g., moderate and no ventilation, the cell covered and uncovered) and different locations of the detectors were investigated to better understand the potential of the detection techniques and challenges in early detection.
Results and Take-Away Message
With the point-type detectors, it was clear that local conditions such as the amount of gas/smoke released and ventilation had a clear impact on the result; i.e., if the gas or smoke does not reach the detector, there will be no detection. Even though identical test setups were used, individual behaviors of the battery cells were observed. Conventional installations with, e.g., smoke and heat detectors, include installation on the ceiling. However, in the current study, it was found that if the gas/smoke was cooled down, e.g., by a steel structure at the ambient temperature, the visible gas/smoke sank and spread along the floor (where detectors are normally not installed). This should be pointed out as a clear challenge in detection.
With the point-type detectors, it was clear that local conditions such as the amount of gas/smoke released and ventilation had a clear impact on the result.
The detectors based on camera techniques performed better in this aspect; they are not limited to their specific point of installation but are able to simultaneously see large areas of a space. As long as the smoke or heat is visible to the camera lens, detection was possible. The outcome of the study with single battery cells is that early detection of thermal runaway could be possible but requires more attention before concluding its efficiency in large spaces such as ro-ro spaces or parking garages.
Sixten Dahlbom
sixten.dahlbom@ri.se
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