HiTHIUM Conducts Groundbreaking Open-Door Fire Test on 6.25MWh LDES System

HiTHIUM Completes Landmark Fire Safety Test for 6.25MWh Long-Duration Energy Storage System

HiTHIUM has successfully carried out what is reported to be the world’s first open-door large-scale fire test involving a 6.25MWh long-duration energy storage (LDES) system powered by kiloampere-hour (kAh) battery cells. The evaluation focused on the company’s ∞Power 6.25MWh 4-hour energy storage platform and was conducted under the full supervision of UL Solutions representatives, U.S. Authorities Having Jurisdiction, and professional fire protection engineers. The testing process adhered strictly to the most recent safety requirements outlined in UL 9540A (2025) and NFPA 855 (2026).

According to test observations, the high-capacity energy storage system demonstrated stable, predictable, and controllable behavior under extreme thermal and fire conditions. The successful validation represents an important advancement in safety verification for high-energy LDES systems and contributes to strengthening the foundation for broader deployment of large-scale energy storage technologies worldwide.

Simulating Extreme Real-World Conditions to Test Safety Limits

This latest test builds upon HiTHIUM’s earlier open-door fire evaluation of a 5MWh system, expanding the scope to validate the higher-capacity ∞Power 6.25MWh platform and its core ∞Cell 1175Ah battery. The objective was to assess safety performance at significantly increased energy levels under highly demanding conditions.

The test configuration intentionally recreated some of the harshest realistic scenarios. Container doors were kept fully open throughout the event to allow maximum oxygen flow, intensifying combustion conditions. Adjacent battery containers were positioned back-to-back and side-by-side with only 15 centimeters of separation, increasing the risk of thermal spread. The system operated at a full 100% state of charge, while all active fire suppression systems were disabled. This approach ensured the evaluation focused entirely on the system’s intrinsic safety design and passive protective features.

Multi-Layer Safety Architecture Put to the Test

To mitigate the complex safety challenges associated with ultra-high-capacity cells and dense energy configurations, HiTHIUM deployed a comprehensive safety framework covering cell-level, module-level, and system-level protections. The testing methodology centered on three key safety objectives: controlled energy release, prevention of fire propagation, and structural integrity under thermal stress.

Controlled Energy Release Without Explosion

Managing thermal runaway in ultra-large 1175Ah battery cells requires careful control of gas and pressure release. HiTHIUM addressed this through a three-dimensional airflow management system with directional venting channels. Additionally, battery modules incorporated a dual pressure-relief valve design to ensure controlled gas discharge. During the fire test, these measures enabled safe and rapid release of internal pressure, preventing explosive events or debris ejection.

Fire Containment Without Thermal Propagation

Despite exposure to intense flames and elevated temperatures under open-door combustion conditions, the system successfully prevented fire spread beyond the affected unit. This was achieved through multiple physical safety barriers, including fire-resistant module covers, reinforced steel enclosures, and thermally insulated multi-layer container structures. As a result, adjacent battery containers remained unaffected, with cell temperatures staying within safe limits and no evidence of cross-container thermal propagation.

Structural Integrity Under Prolonged Heat Exposure

To ensure mechanical stability during extended high-temperature exposure, the ∞Power 6.25MWh system incorporates a reinforced structural design featuring high-strength steel framing, internal stiffeners, and dual-layer partitions. Even after sustained combustion, the tested container maintained its structural integrity, showing no major deformation, collapse, or mechanical failure.

Setting a New Benchmark for Long-Duration Energy Storage Safety

The successful completion of this open-door fire test represents a significant milestone in validating the safety performance of high-capacity LDES systems using kAh battery cells. As energy storage systems continue to scale from 5MWh to 6.25MWh and beyond, rigorous safety validation becomes increasingly critical.

HiTHIUM’s latest test provides valuable evidence supporting the safe deployment of higher-energy storage systems and contributes to advancing industry safety standards. The company has emphasized its ongoing commitment to enhancing reliability through robust engineering design, extreme-condition testing, and continuous innovation.

Looking ahead, HiTHIUM plans to further strengthen its focus on long-duration energy storage as a strategic priority. By actively participating in the development of global safety standards and collaborating with industry partners, the company aims to support the safe, reliable, and scalable adoption of advanced energy storage technologies—helping accelerate the transition toward a more sustainable global energy system.