CATL Opens the World's Largest BESS Testing Facility: Five Labs, $440 Million, Xiamen

The Facility

On May 28, 2026, CATL opened a $440 million, 10-hectare campus in Xiamen with five laboratories purpose-built for testing energy storage systems at full scale — not cells, not modules, but complete containerized systems connected to a simulated grid. Certification bodies TUV SUD, TUV Rheinland, CGC, and CSA are embedded as partners under a “one-test, multi-witness” model, where multiple certifiers observe and validate a single test run simultaneously. CATL describes it as open infrastructure, available to the broader industry.

CATL cites two statistics: nearly one in five large-scale energy storage stations worldwide are underperforming, and 46.5% of systems experience grid-connection delays exceeding two months.

Most energy storage testing takes place at the cell or module level: a cell is tested for thermal runaway behaviour, a module for safety certification. When hundreds of modules are assembled into a containerized system, connected to a power conversion system, and integrated into a live grid, additional failure modes apply — electromagnetic interference, harmonic interactions, thermal behavior under real cycling profiles, and fire propagation between units.

For comparison, NREL’s Energy Systems Integration Facility in the US operates a 13.8 kV / 7 MVA grid-connected storage testing platform. UL Solutions and independent labs such as DNV offer component and module-level certification. CATL describes ESVL as the world’s largest energy storage testbed, combining grid simulation, full-scale fire testing, high-voltage safety, environmental stress, and EMC testing for complete containerized systems on one site.

The UL 9540A shift

On March 13, 2026, UL Solutions published the 6th edition of UL 9540A, the safety standard for energy storage systems in the US market. The revision changes the scope of fire testing.

Previous editions focused on cell and module-level thermal runaway behavior. The 6th edition now explicitly requires testing that demonstrates whether a fire will propagate between energy storage system units — not just within a single module. It introduces formal pass/fail criteria for the first time, with non-propagation between adjacent units as a certification requirement.

The 2026 edition of NFPA 855 makes large-scale fire testing (LSFT) mandatory, aligning with these UL 9540A changes.

As Dana Parmenter of CSA Group noted, previous testing approaches were “really leaving a lot of uncertainty from a safety standpoint” regarding full-engulfment scenarios. The new requirements cover container-scale combustion testing of the type CATL’s thermal safety laboratory is designed to perform.

Grid Integration and Thermal Safety Laboratories

ESVL houses five laboratories.

Grid Integration

The lab houses a 35 kV / 100 MVA grid simulator; derived from the two figures, that is roughly 14 times the MVA capacity of NREL’s 13.8 kV / 7 MVA platform. It can test 10 or more large-scale containers simultaneously against simulated grid conditions, including 1,000-node grid topologies across a 15–60 Hz frequency range.

This covers testing of system behavior during grid faults, frequency deviations, and multi-unit interactions.

Thermal Safety and Combustion

The lab features a 20 MW calorimeter and 100,000 cubic meters of indoor combustion space — enough to test nine large energy storage containers simultaneously.

This is purpose-built for the kind of large-scale fire testing that UL 9540A 6th edition and NFPA 855 now require. Full thermal runaway propagation from cell to module to container to adjacent containers, under controlled and instrumented conditions. The indoor setting eliminates weather variables that complicate outdoor burn tests.

Thermal propagation behavior between containers is the input used to set separation distance requirements and suppression system design under NFPA 855.

The remaining three labs

The facility also includes a high-voltage safety laboratory (1 kV to 500 kV — lightning impulse, withstand voltage, and partial discharge testing), an environmental reliability laboratory (-50 to 100 degrees C, altitude simulation to 7,200 m, salt spray, rain, and sand chambers), and what CATL claims is the world’s only electromagnetic compatibility laboratory capable of accommodating a full 40-foot container (65-ton turntable, 5 MW power supply, anechoic chamber under real charge/discharge conditions).

Ownership and Certification Partners

ESVL is funded and operated by CATL. Four certification bodies — TUV SUD, TUV Rheinland, CGC, and CSA — are partners under the “one-test, multi-witness” model, in which multiple certifiers observe and validate a single test run simultaneously. CATL states the facility is open to the global energy storage industry.

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