Abstract: Based on the actual project requirements of a echelon battery energy storage system, combined with the thermal runaway mechanism of lithium iron phosphate battery, a multi-level warning system and hierarchical early warning strategy based on VOC, combustible gas, temperature, smoke, etc. were proposed to monitor the battery in a full cycle and continuous manner to ensure the rapid and effective detection of battery thermal runaway state and realize the early intervention of fire extinguishing system. Considering the characteristics of low cost, poor safety and reignition of battery fire, a water spray fire extinguishing system was added to the traditional heptafluoropropane fire extinguishing system to ensure the complete extinguishing of the fire. Finally, the effectiveness of the fire warning system was verified by taking the thermal runaway of retired lithium iron phosphate battery as an example.

Key words: battery energy storage system, thermal runaway, multi-level fire warning system, hierarchical early warning strategy, reignition