HEFEI – October 21, 2026 -- Sungrow's PowerTitan 3.0 battery energy storage system contained a thermal runaway event that reached 1259.8°C without spreading to adjacent containers or a medium-voltage substation, becoming the first stacked-cell BESS with an AC-block design to complete a large-scale fire test under UL 9540A: 2026 and CSA/ANSI C800-2025.
UL Solutions conducted the test. Fire Risk Alliance witnessed it and Jensen Hughes observed it. All three PowerTitan generations, 1.0 through 3.0, passed their large-scale fire tests on the first attempt.
Test layout replicated a utility-scale installation with 28.56 MWh of storage
The setup mirrored a block-level utility-scale layout. It included 28.56 MWh of fully liquid-cooled PowerTitan 3.0 units and a 7.4 MW medium-voltage substation. PowerTitan 3.0 combines stacked high-energy-density cells and the DC/AC power converter unit in a single 20-foot container.
Sungrow and the test partners set demanding conditions:
- The system was at 100% state of charge.
- The initiating container and the adjacent container were installed closely, back-to-back.
- All active fire suppression and thermal management systems were disabled.
- Rooftop pressure-relief panels on the initiating container were fully opened to maximize ventilation and oxygen availability.
All smoke and fire effluent was collected and routed through a dedicated purification system. No untreated smoke was released into the environment.
Fire stayed inside Container A during a 7.5-hour burn
The test ran for 7.5 hours under uninterrupted monitoring. Peak internal temperature in the initiating container, Container A, hit 1259.8°C. The highest cell temperature in the adjacent containers stayed below the thermal runaway threshold defined in UL 9540A: 2026.
Container A remained structurally intact. Adjacent Containers B, C, D and E showed no deformation. After the test, the container could still be lifted as a complete unit.
Simulation of hundreds of scenarios matched the physical fire
Before the physical test, PowerTitan 3.0 went through simulation-based assessments across hundreds of application scenarios and operating conditions. Sungrow ran them on its own simulation platform, which it describes as the world's largest of its kind. Simulated fire intensity and development trends closely matched those observed in the physical test. The three completed generations of tests have given Sungrow a database of thermal runaway and fire behavior.
Roger Li, General Manager of the Utility-Scale Product Line at Sungrow's Energy Storage Business Unit, said safety must be engineered in from the start and that storage safety depends on cell performance, system integration, thermal management, structural protection and engineering design together, not on cells alone.
Benjamin Liu, Engineering Manager at UL Solutions, said the design contained the fire and prevented propagation, helping significantly reduce the potential scale of loss.
Sungrow says the results give project owners, investors, insurers and emergency responders a stronger technical basis for assessing fire risk, planning emergency response and protecting assets across a project's lifecycle.