Fortress Power’s eVault Max has passed UL 9540(A), the industry’s most stringent fire safety and large-scale fire test.
Fortress Power is among a select few lithium iron phosphate (LiFeP04) battery manufacturers to pass the UL 9540(A) large-scale fire test. The UL 9540(A) large fire test is the industry’s gold-standard testing method for evaluating thermal runaway fire propagation in a battery energy storage system (BESS). This test was developed to address safety concerns identified by the building codes and the fire service in the United States.
The current International Code Council (ICC) International Fire Code (ICC IFC-2021) allows an individual BESS unit not to exceed 50 kWh and to have a maximum quantity of systems totaling 600 kWh of energy per indoor fire area (battery room) or outdoor, near exposures. It also limits individual residential systems not to exceed 20kWh and to have a maximum quantity of up to 80 kWh.
A critical component of the UL 9540(A) test method is that the abuse of systems continues until system failure.
Typically, heating single or multiple cells at 5°C/minute results in thermal runaway. By abusing the smallest repeat unit of the system, the test is understanding the extent to which that failure propagates. While in operation, a battery management system (BMS) would likely detect temperature or voltage anomalies.
UL 9540(A) test methods assume these systems are non-functional and that cells in the battery pack have reached thermal runaway. In doing so, it judges the systems’ capability at responding to thermal runaway. In fact, the battery pack level test is designed around figuring out how to repeatedly force the battery to fail.
If one or multiple Fortress Power battery cells run into thermal runaway, it will not cause the whole battery pack to catch fire. Fortress Power’s eVault Max unit only generates smoke after four hours of heating with the cell temperature reaching over 250°F (120°C). The battery pack stabilizes, and the temperature drops back to 95°F (35°C) in only five hours.