Full-scale experimental investigation of distinct thermal runaway propagation mechanisms and fire development in lithium-ion battery energy storage cabinets

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Thermal runaway propagation and fire escalation in battery energy storage systems remain critical concerns, yet the role of sustained flaming in altering heat transfer and propagation under realistic cabinet conditions is not fully understood. This study investigates two full- scale BESS cabinets tests under identical triggering conditions, representing flaming and non-flaming scenarios, to clarify the transition from localized thermal runaway to extensive cabinet fire. The temperature, radiant heat flux, heat release rate, total heat release, gas concentrations, and flame evolution were jointly analyzed. Under the non-flaming scenario, only four cells undergo TR and propagation remains localized in a single-chain pattern, whereas sustained flaming strengthens and spatially extends thermal feedback, enabling more cells to be heated simultaneously or in rapid succession and promoting multi-branch cascading propagation. These results reveal distinct multi-physics propagation modes governed by the coupled evolution of gas release, combustion, thermal feedback, and TR propagation, providing an experimental basis for improving early warning, thermal protection, and fire safety design of BESS cabinets.