Abstract
Three installation-level lithium-ion battery (LIB) energy storage system (ESS) tests were conducted to the specifications of the UL 9540A standard test method [1]. Each test included a mocked-up initiating ESS unit rack and two target ESS unit racks installed within a standard size 6.06 m (20 ft) International Organization for Standardization (ISO) container. All tests were conducted with an identical LIB configuration. The initiating unit rack included nine modules (2,430 individual 18650 form factor cells) with a total capacity of 28.9 kWh. The target unit racks were loaded to one-third capacity of the initiating unit with nine partial modules and a total capacity of 9.6 kWh. All cells in the container were charged to 100% state-of-charge and none were electrically connected. Within the initiating mock-up unit, a flexible film heater was wrapped around an individual 18650 form factor cell. This instrumented 18650 cell was heated at a rate of 6°C/min to initiate thermal runaway. Test 1 was a baseline performance test and did not utilize any active fire suppression systems. Test 2 included a Novec 1230 system designed for an 8.3 vol% concentration discharged upon activation of two smoke detectors installed inside the container. Test 3 incorporated a dry pipe water suppression system to provide a uniform 20.8 mm/min (0.5 gpm/ft(2)) spray density delivered at the top of the ESS unit enclosures. Thermocouples were used to measure the cell temperatures in the initiating unit rack and module surface temperatures for the initiating unit and target unit racks. Thermocouples were located throughout the ISO container to measure gas temperatures and wall temperatures. Schmidt-Boelter heat flux gauges were installed to measure incident heat flux to each of the target unit racks as well as the walls adjacent to the initiating rack. Smoke detectors and smoke obscuration meters were used to identify the presence of smoke and characterize opacity of the smoke in the container. Various laboratory- and industrial-grade sensors were used to characterize the gas composition throughout container.