Evaluation of Off-Gas Detection in Li-ion Battery Energy Storage Systems

This paper presents the details and results of laboratory tests conducted to evaluate the potential of off-gas detection systems in providing early warning of thermal runaway (TR) of Li-ion cells. A chemi-resistive based sensor was evaluated in this study. Tests included overheating and overcharging at a constant rate on single cells, and a battery pack. Rack-level tests were also conducted to simulate the effect of real-world installation conditions. In all tests, the sensor gave reliable indication of off-gases. Termination of abuse condition upon gas detection generally resulted in prevention of TR. However, for rapid abuse situations, TR cannot be avoided even though the sensor would provide an early indication of the abnormal condition. The performance of other detectors, which may use sensing technologies targeting different gaseous species, is unknown at this time and will have to be evaluated through follow-up testing. Off-gas detection systems cannot assist in preventing TR when the failure mode involves internal cell failure or mechanical damage. These systems will provide an indication of off-gas and impending TR but will not yield actionable information to prevent the latter. Hence, these detectors, when installed in Li-ion battery systems, will help reduce the likelihood of TRs, but they cannot assist in preventing TR from certain failure modes.