Researchers Complete Experiments Investigating the Effectiveness of Water Suppression on Electric Vehicle Fires
Earlier this year, the Fire Safety Research Institute (FSRI), part of UL Research Institutes, completed experiments to understand electric vehicle (EV) fire behavior. Following initial data analysis and input from the project’s technical panel, FSRI completed the second phase of experiments in November at UL’s Northbrook, IL indoor laboratory to investigate water suppression techniques on EV fires.
During this phase of the Fire Safety of Batteries and Electric Vehicles research project, FSRI aims to understand what water suppression strategies firefighters can use to mitigate demonstrated hazards of EV fires. This phase also seeks to understand the chemical constituents creating occupational exposures, how effective PPE is against these exposures, the effectiveness of PPE cleaning methods, and the potential environmental impact of contaminated suppression water runoff.
Using EV Fire Scenarios to Investigate Water Suppression Effectiveness
To test water suppression strategies, FSRI researchers designed four (4) experiments to match a representative EV fire scenario firefighters would encounter on the fireground. Before the experiments, each EV battery pack was charged to 100% to simulate the conditions under which thermal runaway propagation would be severe and a greater challenge to control or extinguish. A premixed burner was placed below the battery pack and remained in operation until the lithium-ion battery pack heated enough to experience thermal runaway propagation. From this point, the resulting fire was allowed to develop to simulate the typical fire service response and setup time.
Manual suppression was initiated seven minutes after the confirmation of thermal runaway propagation. During each experiment, firefighters included size-up before and during water suppression. Suppression began with typical internal combustion engine car fire tactics, focusing primarily on the vehicle cabin fire. Water suppression was attempted when battery involvement was identified as clearly separate from vehicle cabin/chassis involvement. After ten minutes of on-scene time, the EV was titled using a lift to simulate firefighters working to improve battery pack access for water suppression. The vehicles were held in this position and monitored for any further gas release or thermal energy generation activity.
Measuring EV Battery Damage and Stranded Energy Dissipation
Both routine and innovative fire measurement instrumentation was used to collect data related to heat flux and lithium-ion battery stranded energy dissipation.
- Heat flux gauges were placed 9 feet from the vehicle to measure thermal stress to adjacent exposures.
- Thermal imaging cameras were employed to monitor thermal runaway, battery pack cooling during suppression, and any reignition activity.
- Following experiments, research partners from Munro & Associates safely removed, opened, and analyzed battery pack conditions. FSRI staff separated modules with stranded energy and placed them in an aqueous sodium bicarbonate solution to dissipate stranded energy. Voltage, temperature, and solution electrical conductivity was monitored for an extended period of time to document and provide a basis for evaluation of the feasibility of this means of stranded energy dissipation.
“We look forward to developing tactical considerations through thorough analysis of the suppression experiment data with the members of our technical panel. Use of hose streams demonstrated the challenge in accessing cells in thermal runaway inside the pack, which are well protected under the vehicles. Despite that challenge, it was possible to interrupt thermal runaway in two cases and some promising results were observed for controlling, if not extinguishing, the fires.”
—Adam Barowy, lead research engineer, FSRI
Following data analysis, findings from this experiment phase will contribute to future tactical considerations and training resources to help enable the fire service to conduct safe and effective size-up and suppression strategies.
