EV Battery Fire in an Underground Garage
At 23:40 a fire in an underground parking garage involves a 2022 battery-electric vehicle connected to a Level 2 charger. The fire is extinguished by sprinklers and fire department; the vehicle's front trunk and undercarriage are burned. Six hours later the vehicle rekindles and is extinguished again. The garage has a CO detection system but no dedicated EV suppression. The charger cable is damaged, and the charge port shows melting. The battery pack has a vented cell. The charger log shows charging completed 45 minutes before ignition, but the cable remained connected. The garage temperature was 32°C. The investigator must determine whether the fire originated in the vehicle battery, the charging equipment, or elsewhere. NFPA 1033 requires knowledge of vehicle systems and scene safety.
1. What safety and evidence-preservation steps must be taken before examining the vehicle?
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The vehicle should be isolated in a well-ventilated area, monitored with a thermal imager and gas detector, and kept away from combustible materials because lithium-ion batteries can rekindle hours or days later. The investigator should wear appropriate PPE, including respiratory protection, and use a documented safety plan. Before moving the vehicle, they should photograph the scene, the charger, and the vehicle in place; record the charger log and vehicle state of charge if accessible; and preserve the charging cable and EVSE. The vehicle should not be moved until the battery is confirmed stable or the manufacturer's emergency response guide is followed. NFPA 1033 requires scene safety and evidence preservation. Any discharge water and debris should be contained because it may be contaminated. The investigator should also coordinate with the utility and the vehicle manufacturer.
2. How would you determine whether the charging equipment or the battery caused the fire?
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The investigator should examine the charge port and cable for melting, arcing, and mechanical damage, and compare the damage to the charger log. If charging completed 45 minutes before ignition but the cable remained connected, the EVSE could still have been energized. The investigator should download EVSE fault data, check the vehicle's battery management system for cell voltage and temperature anomalies, and look for thermal runaway indicators such as a vented cell, swollen modules, and ejected material. Fire patterns that begin at the charge port and extend into the battery support a charging-equipment origin; patterns that begin inside the battery pack and vent through the undercarriage support a battery origin. NFPA 1033 requires knowledge of vehicle systems. Laboratory analysis of the battery and charger, plus review of the manufacturer's data, is needed before a cause is assigned.
3. What does the six-hour rekindle suggest, and how should it affect the investigation?
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A rekindle six hours later is consistent with a lithium-ion battery fire, where damaged cells can undergo delayed thermal runaway. It does not by itself prove the battery caused the original fire, but it raises the probability that the battery was involved. The investigator should document the rekindle, the firefighting methods, and any battery monitoring data. They should treat the vehicle as evidence and not release it until the battery is stable and the examination is complete. The rekindle also affects scene safety and may require a second scene examination. NFPA 1033 requires the investigator to consider fire dynamics and scene safety. The final cause should integrate the rekindle with the origin patterns, charger data, and laboratory results, rather than relying on the rekindle alone.