People often hear that electric vehicles are not more prone to fires than those powered by internal combustion engines (ICE). As much as that is still debatable, it is not the main reason for concern. When a battery pack catches fire, the real problem is that it is almost impossible to kill, as a recent incident with a Tesla Model X graphically demonstrates.
On October 1, a Tesla Model X attempted to back a jet ski into the water at the Polk Street Boat Ramp in Hollywood, Florida. According to the Hollywood Professional Firefighters, the SUV"lost traction and slid into the inter-coastal." When it was already submerged, "the salt water reacted with the vehicle's electronics, causing them to short, sparking a fire that burned underwater for an extended period of time." There are a lot of problems with that report.
First of all, the Hollywood Professional Firefighters identified the battery electric vehicle (BEV) as a Model S, which the videos show was not the case. The Falcon doors that can be seen underwater belong to a Model X.
The second issue is supposing that the car lost traction and slid into the water. According to another video recorded about the incident, a woman was driving the Model X while her husband unloaded the jet ski from the trailer. That was when "a warning label came on," telling her to get out of the car, which she couldn't do. Either the 12V battery had failed, which made the electronic locks stop working, or the battery pack was already facing some sort of issue, also interfering with the door operation.
Photo: via StacheD Training
The woman's husband had to rescue her with the jet ski, but it is not clear if she managed to open the door, if they had to break a window for her to escape, or if the Falcon doors opened and allowed her to leave the cabin. The submerged Model X shows not only the rear doors upward but also the rear hatch. Whatever happened, it suggests that the BEV only slid into the inter-coastal because it already had a malfunction.
The final issue is supposing that the salt water caused the thermal runaway. If the woman driving the Model X received a warning about issues, it is not unlikely that the battery pack was already experiencing issues before it hit the sea. In that case, the seawater's role was just not managing to kill the blaze, not causing it.
After addressing these issues, we can focus on the most critical element that this situation presents. Although it also exposes Tesla's problems, it is a powerful demonstration of what happens in a thermal runaway. The Hollywood Professional Firefighters stress that the Model X "burned underwater for an extended period of time." Unfortunately, that is very vague. It would be interesting to learn how long this waterproof blaze took to end. Whether it was for an hour or four, it clearly shows why battery pack fires are extremely dangerous.
Photo: via StacheD Training
Ternary lithium-ion cells use oxides in their composition. That means they have their own oxygen and do not need the gas in the air to keep a fire lit regardless of the conditions. The main goal of throwing water on a blaze is to cut access to oxygen. All other materials used to extinguish fires have the same purpose. When it comes to lithium-ion cells, water only helps to cool down the burning materials and try to bring the situation to an end. The episode in Florida reveals beyond doubt that it is far from effective.
While discussing the case for his StacheD Training YouTube channel, Captain Durham found two other episodes where putting a vessel on the water also saw thermal runaway episodes. On February 13, 2022, Tom Powell shared on Facebook another underwater fire involving a Model X. The vehicle was in the Balearic Islands, Spain. The other case involves a Mitsubishi Outlander PHEV – or plug-in hybrid electric vehicle, as you are probably aware. We have no idea what caused the fires, but the other Model X blaze also occurred while the BEV was submerged.
Photo: Tom Powell/Boat Fails
This is why the Hollywood Professional Firefighters said that electric vehicle fires pose "a whole new level of hazard to the Fire Service, causing Fire Departments worldwide to rethink how they mitigate electric vehicle emergencies." Apart from not dying even underwater, these fires can also reignite without warning, even days after the initial incident.
The videos below show these waterproof blazes and how impressive it is to have something burning "for an extended period of time" under these conditions. It is worth remembering that a 100-kWh battery pack contains the equivalent of 3 gallons (11.4 liters) of gasoline in terms of energy. That does not mean it will not burn persistently and with severe consequences to anything or anyone around them – especially those who have no one to help them escape cars with electronic door handles.
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