HiTHIUM, a global energy storage technology company, said that it has successfully completed the world’s first open-door fire safety test of a large-scale battery energy storage system (BESS) equipped with high-capacity battery cells. The system tested was the company’s ∞Power 6.25 megawatt-hour (MWh) long-duration energy storage unit, which uses kiloampere-hour (kAh) lithium-ion battery cells.
The test was carried out under the supervision of representatives from UL Solutions, U.S. Authorities Having Jurisdiction and certified fire protection engineers. HiTHIUM said the trial was designed to meet the latest safety standards, adhering to the 2025 edition of UL 9540A and the 2026 revision of NFPA 855, industry benchmarks for battery system fire testing and risk assessment.
Unlike conventional fire safety tests, HiTHIUM conducted this validation with all container doors fully open to maximize oxygen flow and simulate extreme real-world fire conditions. Adjacent BESS units were placed as close as 15 centimeters apart and the system was charged to 100 percent state of charge, with all fire suppression systems intentionally disabled.
The company said its multi-layered safety design successfully met three core safety challenges: managing release of thermal energy without explosion, containing combustion without propagation to adjacent units, and maintaining structural stability under prolonged high heat exposure. HiTHIUM reported no explosions, no spread of fire to neighboring systems and no significant deformation to the test unit’s structural frame.
HiTHIUM executives called the outcome a milestone in safety verification for large-scale, high-energy storage systems. The test builds on the company’s previous open-door fire validation at lower energy levels and is intended to strengthen confidence in deploying long-duration energy storage at utility and grid scales.
Analysts say rigorous safety testing is critical as energy storage systems are increasingly used to support renewable power generation and stabilize electrical grids worldwide. HiTHIUM said it will continue advancing safety standards and working with industry partners to improve both technology and testing frameworks for next-generation energy storage.
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