BESS thermal runaway behaves very differently once flames appear, according to a Journal of Energy Storage paper that ran two full scale cabinet tests under identical triggering conditions, one that flamed and one that did not. The work went online on 20 October 2026 in volume 183 (DOI 10.1016/j.est.2026.125130) and measured temperature, radiant heat flux, heat release rate, total heat release, gas concentrations and flame evolution.
BESS thermal runaway without flames
In the non flaming test only four cells went into thermal runaway, and the event stayed localised along a single propagation chain. The cabinet absorbed the failure without the spread seen in the other test.
BESS thermal runaway with flames
In the flaming test the authors report strengthened and extended thermal feedback. More cells were heated at the same time or in rapid succession, and propagation became a multi branch cascade rather than a single chain. According to the abstract, this fire feedback accelerated escalation to a full cabinet fire.
| Aspect | Non flaming test | Flaming test |
|---|---|---|
| Cells in thermal runaway | Only four | More cells, heated simultaneously or in rapid succession |
| Propagation pattern | Localised, single chain | Multi branch cascade |
| Thermal feedback | Not described as strengthened | Strengthened and extended |
| Outcome | Not described as a cabinet fire | Fire feedback accelerated escalation to a cabinet fire |
What the abstract does not say
The abstract does not give the cell chemistry, cabinet capacity, cell count, trigger method or the heat release values, and it does not explain why one of the two identical tests produced flames. Those details determine how far the findings transfer to other products, so the full paper matters for anyone using it in a safety case.
The result still carries a clear design message for BESS thermal runaway protection: stopping a flame from forming may matter as much as stopping the first cell from failing, because flame feedback turned a four cell event into a cabinet fire. Operators are building at pace, as seen when Nightpeak’s Bocanova 2 battery storage came online in ERCOT, and fire behaviour inside cabinets is one input to how such sites are spaced and protected. Thermal design is the other, as covered in our heat pipe battery thermal management report.
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