Fluence completes UL-rated fire safety tests of Gridstack Pro 5000
Battery energy storage integrator and optimization software company Fluence has partnered with CSA Group, a leading product testing, inspection, and certification organization, to test the safety of the Gridstack Pro 5000.
After rigorous testing of one of the highest-density battery storage solutions in the market, Fluence’s test results exceeded existing safety standards (UL 9540A) and set a measurables for forthcoming industry regulations, including the 2026 NFPA 855 standard.
Fluence’s Gridstack Pro 5000, delivering up to 5.6 MWh in a 20-foot enclosure, underwent both fire and explosion testing at Safe Laboratories in North Carolina. The tests were observed by CSA Group and independent subject matter experts, including members from Hiller. The system successfully demonstrated that it could prevent thermal runaway propagation and withstand worst-case scenarios without the use of fire suppression or firefighting intervention.
The large-scale tests were conducted in four enclosures containing live batteries, spaced at industry minimums, and a fire was deliberately ignited in the center enclosure. The fire did not spread to adjacent enclosures, proving the integrity of the system’s safety design.
Peter Williams, Fluence SVP and Chief Product and Supply Chain Officer, stated that the company was looking ahead to next-generation systems when looking to exceed current safety standards.
“We designed Gridstack Pro 5000 to push the boundaries of what is possible in energy storage density, and with that comes a responsibility to prove it can be done safely,” Williams said.
“This testing goes far beyond what the industry currently requires and is not only a validation of our design, but a real-world demonstration of how next-generation systems must perform under worst-case scenarios.”
Since 2022, Fluence made safety advancements efforts in energy storage testing, collaborating with laboratories aiming to prevent, detect and contain thermal events, while maximizing energy capacity.
Hiller VP of Energy Infrastructure, Fire Protection Engineer, Paul Hayes, praised Fluence for their commitment to exceed current and meet requirements for future safety standards.
“Fluence continues to show its commitment to fire safety by going above and beyond industry standards,” Hayes said.
“The scale and extent of their testing demonstrate readiness to meet the requirements of the upcoming 2026 NFPA 855 safety standard ahead of publication. Gridstack Pro 5000’s successful performance under multiple physical test scenarios confirms the system’s safety architecture and Fluence’s commitment to industry safety standards.”
Beyond fire testing, Fluence collected detailed gas sampling data to support emergency response planning, first responder training, and regulatory guidance.
The industry at large continues to show off their fire safety testing, while standards organizations are also competing to show deeper and more rounded fire safety protocols. Multiple large-scale battery companies have also been using CSA Group’s own TS-800 large-scale fire test protocol for energy storage systems.
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