Shanghai – September 07, 2026 -- APsystems' liquid-cooled commercial and industrial energy storage system, APstorage 261L, has passed the UL 9540A fire propagation test under the supervision of TÜV Rheinland, containing thermal runaway entirely within a single cabinet during the trial.

Test results exceed industry safety thresholds

During testing at 100% state of charge with the fire suppression system deliberately disabled, the APstorage 261L cabinet showed no short circuit, fire spread or explosion, and its structure remained intact throughout. Heat flux near the tested cabinet measured 0 kW/m2, well below the UL 9540A threshold of 1.3 kW/m2 that flags ignition risk to neighboring equipment via thermal radiation.

The maximum surface temperature recorded on the tested module and adjacent modules was 83.9°C, confirming that thermal propagation was stopped between modules. The maximum temperature on the neighboring wall reached only 30.6°C, just 3.1°C above ambient conditions.

System architecture layers four levels of fire protection

APstorage 261L uses a single-cluster liquid-cooling architecture that keeps inter-cell temperature differences below 3°C, a design intended to extend battery life and improve operational safety. The system combines a four-tier fire protection system, active ventilation and passive pressure-relief mechanisms into a multi-layer safeguard extending from cell level to full installation.

Compact footprint targets fast-deploying European C&I projects

The unit occupies just 1.3 square meters and uses plug-and-play connectors to simplify installation and commissioning. Its modular design allows parallel expansion with additional cabinets, suited to industrial plants, commercial facilities and combined solar-storage-EV charging installations.

APsystems supports the product through its European distribution network and a warehouse in the Netherlands dedicated to commercial and industrial customers, providing product availability, training and on-site technical support.