Hithium completes open-door fire test of 5MWh energy storage system

Hithium reports battery safety test results in China

Hithium has announced the results of a large-scale open-door fire test for its ∞Block 5MWh energy storage system, conducted under extreme conditions in China.

The company released the data at the 18th SNEC event on 11 June 2025, where it also received fire test certification from UL Solutions.

According to Hithium, the trial involved a deliberate thermal runaway event to assess safety features across four connected containers under high heat and open airflow.

The test ran for 15 hours and, according to Hithium, confirmed no fire spread beyond the initiating container.

The company said the outcome was based on its multi-layer safety design, which includes temperature-resistant materials, insulation, and structural containment.

Test procedure exposed battery systems to high heat

The fire test scenario was triggered by overheating eight battery cells in one container, known as Container A, leading to ignition and combustion.

According to Hithium, ignition was initiated by opening pressure relief valves and releasing flammable gas, which was then ignited under fully open-door conditions to allow maximum airflow.

The fire exposed adjacent containers B, C, and D to direct heat without triggering thermal runaway.

Hithium reported peak temperatures of 1,372°C at the four-hour mark, but stated that temperatures in the adjacent containers stayed well below critical thresholds.

The company said that no structural collapse occurred, and that battery modules in the surrounding containers remained unaffected.

UL Solutions presents fire safety certification

UL Solutions awarded Hithium a certification acknowledging the system’s performance against UL 9540A and NFPA 855 safety criteria.

Qifeng Xiao, General Manager of the Energy and Automation Division, Asia Pacific at UL Solutions, said:

“Hithium’s pioneering open-door extreme fire test was the first to be conducted under full oxygen exposure—far beyond the industry standard closed-door with explosion vent fire test model.

“Hithium’s pioneering open-door extreme fire test was the first to be conducted under full oxygen exposure—far beyond the industry standard closed-door with explosion vent fire test model.

“The positive outcome not only validated the system’s self-contained fire protection, but also established a valuable reference for the development of global energy storage safety standards through the world’s first open-door fire test.”

The company stated that the certification followed evaluation of system behaviour across multiple fire conditions.

Safety system includes multi-layer fire protection design

Hithium said its test results reflected a system-wide safety architecture designed to limit propagation and maintain structural stability.

At the cell level, the manufacturer highlighted the use of thermal-resistant electrode materials and flame retardant components.

At the module level, low conductivity insulation and top covers were used to contain potential fires.

For the container structure, the company cited heat-resistant construction and high-strength frames to preserve integrity under extended exposure.

According to Hithium, this combination allowed the initiating container to burn without affecting adjacent storage units.

Open-door testing offers data for future standards

Hithium presented the open-door testing approach as an alternative to the more common closed-door fire models used in the industry.

The company said its approach provided a more challenging scenario by allowing full oxygen flow throughout the test.

It argued that this setting generated higher thermal exposure and more closely replicated potential real-world hazards.

A video of the test was shown during the company’s presentation at SNEC, where technical staff outlined the method and reviewed results.

Hithium stated that the event aimed to contribute to improved global energy storage safety benchmarks.

Hithium completes open-door fire test of 5MWh energy storage system: Summary

Hithium conducted an open-door fire test of its ∞Block 5MWh energy storage system.

The test took place in China and was announced at the 18th SNEC on 11 June 2025.

The fire was triggered by inducing thermal runaway in battery cells inside one container.

The test ran for 15 hours under full oxygen exposure with fire suppression disabled.

Temperatures peaked at 1,372°C during the fourth hour.

No fire propagation occurred to adjacent containers B, C, or D.

Cell temperatures in the adjacent containers remained below critical levels.

No structural failure or internal battery damage was recorded in non-igniting containers.

The test conditions included 100% State of Charge and 15 cm spacing between units.

UL Solutions awarded Hithium fire test certification for compliance with UL 9540A and NFPA 855.

Hithium stated that its multi-level fire safety architecture enabled the system to withstand the extreme test scenario.