Full-scale room fire of Li-ion battery modules undergoing thermal runaway

The integration of high-energy lithium-ion batteries (LIBs) as energy storage solutions is increasing in the building sector (e.g., residential, schools, offices, commercial and industrial buildings). This increases the fire load, raising fire safety concerns, including characteristic fire behaviour, increased fire intensity, faster fire growth, prolonged burning duration, fire spread and flashover risk. Full-scale fire experiments with NMC battery modules of nominal 6600 Wh were conducted in an ISO 9705 compartment. The emphasis of the work was to analyse the fire characteristics within the room from the beginning of thermal runaway in a set of individual cells and continuous cell-to-cell thermal propagation in a single module. The results revealed that simultaneous cells in thermal runaway within a module intensified heat release into the room. The fire development differed from fires in common technical rooms, exhibiting flash fire, ultra-fast fire growth, intense thermal feedback and multiple heat release rate peaks. The experimental findings provide critical data to support risk assessments of battery energy storage systems. Currently, the lack of guidelines on fire safety requirements for battery rooms limits the ability to design rooms with appropriate active and passive fire safety measures. Future research should further explore fire spread between modules and the effectiveness of active and passive fire protection measures in confined compartments. • A controlled propane burner heating method is presented to trigger thermal runaway in a battery module. • A case of gas release under thermal runaway conditions with delayed gas ignition was observed. • Simultaneous thermal runaway of multiple cells increased both the temperature and the heat release rate within the room. • The fire was self-sustained due to continuous cell-to-cell propagation. • The fire development phases within a compartment are highlighted. • The growth rate is comparable to the hydrocarbon fire curve during its fully developed stage.