Shanghai – September 07, 2026 -- APsystems' liquid-cooled commercial and industrial (C&I) energy storage unit, the APstorage 261L, has passed the UL 9540A fire propagation test under the supervision of TÜV Rheinland, with thermal runaway fully contained inside a single cabinet during trials.
Test conditions pushed the system to its limits
The APstorage 261L was evaluated at 100% state of charge with its fire suppression system deliberately disabled. No short circuit, fire spread, or explosion occurred, and the cabinet retained its structural integrity throughout the test.
Thermal readings undercut UL 9540A thresholds
Heat flux near the tested cabinet measured 0 kW/m2, well below the UL 9540A limit of 1.3 kW/m2, removing the risk of radiant ignition to adjacent equipment. The maximum module surface temperature reached 83.9°C on both the affected and neighboring modules, indicating thermal propagation between modules was effectively blocked. The maximum temperature on adjacent walls was 30.6°C, just 3.1°C above ambient conditions.
At every tier of testing—cell, module, and cabinet—thermal runaway remained confined to a single enclosure, preventing spread to neighboring cabinets.
Single-cluster liquid cooling limits cell temperature variation to below 3°C
The APstorage 261L's safety architecture combines a single-cluster liquid cooling design with a four-level fire protection system, active ventilation, and passive decompression mechanisms. The cooling architecture keeps cell-level temperature variation under 3°C, extending battery lifespan while reinforcing operational safety.
Compact 1.3 m2 footprint targets rapid C&I deployment across Europe
The system's plug-and-play connections and modular design allow parallel expansion across multiple cabinets, positioning it for industrial facilities, commercial buildings, and solar storage-and-charging applications. APsystems supports the product through a European network and a dedicated C&I energy storage warehouse in the Netherlands, providing local product availability, professional training, and on-site technical support.