Abstract: The variation of characteristic parameters such as the voltage, surface temperature, and released gas concentration of lithium iron phosphate batteries for energy storage under over⁃charge condition were discussed. The thermal runaway mechanism, development process and early warning threshold were analyzed. The experimental results showed that overcharging can lead to a series of exothermic chemical reactions inside the battery,which causes increase in temperature and voltage, accompanied by a large amount of combustible gas production.The H2 is the highest in content in the mixed gas and is detected by the gas detector first. The recommended alarm ranges of battery voltage, surface temperature and H2 concentration are 4.8~6.6 V, 60~116 ℃ and 20~50mg/L, respectively.

Key words: energy storage power station, Li- ion battery, thermal runaway, early warning