Abstract: Since 2020, the auxiliary monitoring system of TA substation has reported "battery room combustible gas detector 107 alarm" for many times. After checking the site, the operation and maintenance workers found that the combustible gas detector in the battery room acted. The signal disappears after starting the indoor exhaust fan. Summarizing the working principle of the battery, the generation reason of combustible gas and relevant fire-fighting knowledge has certain theoretical and practical significance for the operation and maintenance workers to deal with relevant defects.