Large-Scale Fire Testing (LSFT): from best practice to mandatory requirement  

No fire, or no propagation?  

LSFT’s emergence reflects an acceptance that in the unlikely event a BESS fire does happen, the spread is contained to a single unit at the system level, in much the same way that UL9540A assesses the propagation risk of thermal runaway from a single cell.  

In an ideal world, BESS temperature management and fire detection and suppression systems should prevent fires from happening or going beyond a single module. Fire suppression technologies like Etica’s immersion cooling, StatX’s aerosol-based tech or Honeywell’s Li-Ion Tamer off-gas detection systems aim to contribute to reducing fire incidents to near zero.  

With LSFTs, technology providers aim to demonstrate that if systems do fail, there will be no repeat of fires at the Moss Landing or Gateway projects in California, where entire BESS arrays caught fire and burned for days.  

LSFTs aim to ensure that any future fire events are more like the incident at the Thurrock BESS project in the UK, where a single unit caught fire during construction. With close monitoring and a carefully controlled response, the fire was contained, with no risk to the wider community. The site was declared safe by fire teams and handed back to owner Statera within 24 hours. Thurrock BESS went into commercial operation in the second half of 2025.  

“That is the story of BESS fires and the types of loss events that we expect to see for the BESS market going forward,” an insurer said at the time, referencing Thurrock.  

So, who has done them?  

The table below shows notable LSFTs conducted by leading BESS manufacturers and system integrators, using what has been publicly announced and reported on by Energy-Storage.news.  

The list is not comprehensive and as LSFTs become minimum requirements expect more in 2026, possibly between the time of writing and printing.  

The timeline of LSFTs  

Sungrow claimed to have taken a pioneering approach to fire testing with its PowerTitan 1.0 BESS solution in June 2024, conducting a test broadcast live with DNV oversight. It followed this with PowerTitan 2.0 testing in April 2025, featuring a 25-hour burn duration that demonstrated no propagation to neighbouring units. Wärtsilä followed with LSFTs on its products later that year.  

Hithium claimed a significant milestone with its LSFT in June 2025, conducting what it termed the “world’s first all open-door LSFT.” This 15-hour full combustion test at 100% state of charge (SOC) was conducted by UL Solutions. 

Fluence conducted comprehensive testing of its Gridstack Pro 5000 system in June 2025 at SAFE Labs in North Carolina, combining five days of explosion testing with fire testing under CSA Group observation. BYD, Canadian Solar and other providers conducted significant tests throughout 2025.  

A notable omission from the list is Tesla, which has not publicly made any announcements about an LSFT on its Megapack technology. A fire at the Tesla-supplied Victorian Big Battery project in Australia in 2022 during commissioning tests saw one 3MWh Megapack ignite and spread to a neighbouring unit, although it did not propagate further and burned out within six hours, in line with the manufacturer’s guidance.