One, you’d be a fool to trust Tesla used a non-flammable foam. They’ve outright lied about their battery cells and been caught lying about them, and carried on lying. Second, foam does not magically solve for the fact that you have an enclosed space filled with liquids and fatally corroded batteries. If the foam is absorbent, it will actually make things WORSE. Because now you have fatal ruptures AND new shorts AND more corrosion. It’s flood water. Which is inherently contaminated. It’s not pure salt water. It’s a disgusting, corrosive, toxic mix of freshwater, salt water, whatever’s on the ground, biological agents, chemicals and toxins galore, and nothing fun at all. This toxic mix from hell is why flood cars with interior flood water are instant total no matter how ‘light’ the damage. Insurers do not want to cover claims for flesh-eating bacteria. That toxic mélange destroys any sort of seal in short order. Take your pick as to mechanism – your guess is as good as mine. Nobody knows what exactly is in that ‘water.’ We don’t want to. All we need to know is that between pressure, corrosion, and contaminants, your seals are done. Seriously. Don’t go playing in flood water. We also know this water will corrode contacts and metals. We don’t know which, what extent, any of that. Again: it’s mystery liquid. There’s ammonia and ammoniums, propylene and ethylene glycols, new and used petroleum distillates, salts, sulfurs, bromides, and all manner of conduction-enhancing corrosive brews. Then there’s the matter of seal and gasket designs. Seals and gaskets are designed to keep a specific type of fluid inside a specific type of metal or plastic and shrug off a monsoon. They are NOT designed and they are NOT capable of handling long-term submersion. That would require a TOTALLY different design of everything; different metals, different plastics, different gasket materials, the works. If you soak a sealed rear differential in pure isopropyl alcohol for 24+ hours, then you check what’s inside, you’re going to find contamination from the isopropyl alcohol. Going through large puddles and even fording rivers? A-okay. Submerged uninterrupted in a liquid for days? Doesn’t matter what the liquid is, that seal is done. “Oh well just fix the seals! Easy!” We just covered that. It’s not easy. You’re now talking about a battery housing made from high nickel alloys. Stuff like UNS N06601 AKA Alloy 601 AKA Inconel. Easily over triple the price. Twice the thickness and switching to highly insensitive butyls which also cost 2-3x as much. And ultimately the fundamental problem with BEVs is inherent to the design. Everyone puts the batteries below the floor. This means they are the lowest point on the car and the most susceptible to submersion in even passable water. That’s right folks – even standing water which a Tesla Model 3 can (not entirely) safely drive through is more than enough to submerge the battery and seals. How much water exactly? Let me put it this way: it doesn’t even have to reach the bottom of the doors on a BEV. We’re quite literally talking an amount of water that wouldn’t bother a Jeep Wrangler, and even a Toyota Prius would likely survive. Why? Wrangler is obvious – the water didn’t reach anything but wheels and tires. But on the Prius? The secret is simple: the HV system is mounted far higher. Flood waters only touched the floor pan, oil pan, and maybe transmission and axles. The actual HV battery is mounted in the back seat area, above the top of the spare tire well, and inside the weathertight interior. But again: it’s an inherent design flaw that cannot be overcome by anything. Because it’s about weight. The battery is by far the heaviest component of a BEV, and can even weigh more than the unibody. If you want your 4 door sedan with flat floors, and you don’t want it to weigh 10,000lbs thanks to reinforcements, and you also don’t want it to handle like a plate balanced atop a twig? Structural battery floor. That’s the only way it works – regardless of ride height! Ride height is just setting the body higher on the axles with a higher COG. The Hummer EV still uses a structural battery floor which is the lowest part of the car. Get the water over the axle hubs, and that Ultium pack’s now an Ultimate Inferno pack too. I’m not a storm water professional by any stretch. I’m IT and automotive. I live in an area that basically never floods either. But once, we had a storm sewer collapse during torrential rains. This led to localized flooding. And it’s a fairly modern suburban area. The area’s old enough, people absolutely dumped used motor oil, transmission fluid, ethylene glycol, pesticides, and paint right into the brickwork storm sewers. For years. (And well past the point where they knew better. I saw people doing it into the 90’s.) And the fucking stench. Oh. My. Gods. We’re talking maybe a whole four or five inches of water over a thousand square yards at most. And it smelled worse than the contaminated fluids container at the shop. The one we dumped literally anything that wasn’t clean used motor oil in. You have a bright future in marketing. Imagine being the poor sap tasked with breaking these cars apart for recycling. You also get the raw sewage in the car, which has a unique smell all of its own. Once you have smelled sewage you won’t forget it. It always smell the same, so I could walk into a house and know it had a sewage overflow the minute I walked into the basement. Both LV and HV systems do use watertight connectors and sealing at potential entry points, or place intrusions within weathertight areas. As an example, the Chevy Bolt EV (both generations; both the T-pack and the floor pack) locate the HV connections outside of the weather-tight area at the very front of the vehicle and very low to the ground. Well below the underhood electronics in fact. But the connector is double-gasketed. There’s an outer housing for the pass-through which has a watertight gasket, and then the HV cable connections themselves have a gasket as part of the connector. But these assemblies are rated much like your ‘water resistant’ watch; they can only keep water out for X continuous hours at Y, Z, and A variables. You can soak the hell out of the underbody on a Chevy Bolt. You can drive it through several inches of water. You can drive it in a monsoon. Snow and ice from salted roads can get stuck all around it. And in those conditions, the seal will hold. In fact, nearly every sensitive or high current connection on your car which may be exposed to water regularly has similar waterproofing. Even those that don’t necessarily look like it. Those little ‘accordions’ inside your O2 connector? Those actually form a multi-layer water-tight seal. The electrical connectors on modern cars generally have excellent weather resistance or water-tightness. But when you start exposing it to high salinity water for hours or days – especially when that water is full of other nasty chemicals that break down those rubber seals – it’s going to fail. That’s well outside the design envelope. And as everyone will tell you: the safest thing to do if you think there will be flooding is to completely remove the car from the area. Cars are not designed to sit in flood waters, whether they’re ICE, PHEV, or BEV. That’s miles outside what reasonable for anything. If they were, flood totaled cars wouldn’t be a thing. Firefighters would take the big trucks on flood rescues, not low-draft boats. What you see in movies is bullshit. Getting a typical gasoline car to actually catch fire is VERY hard. Set aside flooding. To get a gasoline car to catch fire you need several things to happen. One, you need to have a significant fuel leak. Two, you need to have a sufficiently hot ignition source or significant amount of vapor in an enclosed space. Three, you need to combine these two things. This is actually a LOT harder than people think. Underhood fires occur because you have fuel, enclosed space where vapors collect, and extremely high temperatures. That’s the issue. If you take a car that just got it’s entire rear half sheared off in a collision and has poured the entire contents of it’s gas tank over the road? Fire’s responding “just in case” more than anything. Liquid gasoline doesn’t want to burn easily. It’s the vapors that are on a hair trigger. BEVs (note I’m talking BEVs alone, NOT PHEVs) require only one thing happen to become an impossible to extinguish fire: damage a battery cell. That’s it. If you damage a battery cell in the BEV’s motor power pack, you have fire risk. You don’t need any other thing to occur. You don’t need to puncture the steel housing, you don’t need to apply voltage, you don’t need to add water. All you need is one damaged cell out of hundreds or potentially thousands, and you have a runaway exothermal reaction. Otherwise known as: BIG GODDAMN FIRE. The Tesla cultists love to throw around the false claim that numbers prove ICEs catch on fire more frequently. They don’t. They’re lying with statistics. As a raw number, more ICEs catch on fire, because there are more ICEs on the road. Duh. It’s exactly as absurdist as claiming that because you have 50 hens and 5 roosters, all chickens lay eggs. The question they refuse to answer is: what is the number of fires per miles driven as a share of BEV and as a share of ICE. That is, for each of each type on the road, how many fires occur as a percentage of the population? I’ll give you a hint: EVs in 2018 (the data I gave above) had a total of 208,000 new registrations out of a total of 279,100,000 total registered cars in the US. It will be interesting to see how much of the difference in the prevalence of fires in EVs vs gasoline vehicles changes over time, and whether the difference is largely down to the fact that the fleet of EVs is significantly newer on average. EVs are still new and expensive enough to be far better maintained than the average ICE that catches fire.
