Shanghai – September 07, 2026 -- APsystems' liquid-cooled commercial and industrial (C&I) energy storage system, APstorage 261L, has passed the UL 9540A fire propagation test under supervision from TÜV Rheinland, containing thermal runaway entirely within a single cabinet with no spread to adjacent units.

Test data shows near-zero heat transfer to neighboring equipment

Engineers ran the APstorage 261L at 100% state of charge with its fire suppression system deliberately disabled. Measured heat flux near the affected cabinet registered 0 kW/m2, well below the UL 9540A threshold of 1.3 kW/m2, eliminating radiant ignition risk to adjacent equipment. Peak module surface temperature reached 83.9°C on both the affected and neighboring modules, indicating no inter-module thermal propagation. The maximum adjacent wall temperature hit just 30.6°C, only 3.1°C above ambient.

No short circuit, fire spread, or explosion occurred at any test stage — cell, module, or cabinet — and the unit retained structural integrity throughout.

Four-layer fire protection architecture underpins the design

The APstorage 261L uses a single-cluster liquid-cooling architecture that keeps cell temperature variation below 3°C, extending battery life while improving operational safety. Safety features combine a four-tier fire protection system, active ventilation, and passive pressure-relief mechanisms into a multi-layer defense spanning cell to full installation level.

System targets rapid deployment for European C&I projects

With a footprint of 1.3 square meters, the cabinet features plug-and-play connections for simplified installation and commissioning. Its modular design supports parallel expansion across multiple cabinets, suited for industrial facilities, commercial buildings, and solar-plus-storage applications.

APsystems backs the product with a dedicated C&I energy storage warehouse in the Netherlands and its European distribution network, providing local product availability, technical training, and on-site support.