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SolaX Completes UL-Conducted System-Level Deflagration Test on 5 MWh Energy Storage System

Test conducted under proposed UL 9540A:2025 framework on ORI 5 MWh BESS using real lithium-ion cells

SolaX has completed a full-scale system-level deflagration test on its ORI 5 MWh large-scale battery energy storage system (BESS) under the proposed UL 9540A:2025 framework. UL Solutions was directly involved in the design, execution, and assessment of the test. According to the company, this is the first system-level deflagration test conducted globally by UL under the proposed standard.

The test was carried out on a fully integrated 5 MWh system using real lithium-ion battery cells. Under controlled conditions, selected cells were intentionally driven into thermal runaway while the emergency ventilation system remained closed. The setup enabled the system to undergo flammable gas release, accumulation, and deflagration, replicating a worst-case system-level scenario.

UL Solutions designed the test site, system configuration, and operating conditions based on simulation studies. The trigger point was positioned in an area identified as prone to stronger pressure waves and flame turbulence, increasing stress on the container’s structural integrity and pressure-relief mechanisms.

According to test observations, the pressure-relief structure activated as designed. The container doors remained closed without significant deformation, and the container structure remained intact with no rupture. No components or structural fragments were ejected, and no additional risks to personnel or the surrounding environment were identified.

An engineer from UL Solutions involved in the test stated that the scenario was designed to maximise both severity and realism, incorporating redundant ignition sources and a defined trigger-cell initiation mode to increase deflagration potential. SolaX said it will continue working with UL Solutions and other international organisations to advance system-level safety testing for large-scale energy storage systems.