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Comment by Someone1234 | Hacker News Reader

I have to admit I under-estimated how problematic electric vehicle fires would be based on my knowledge with smaller lithium-ion devices like phones (that just pop and quickly fizzle out). But after reading about fire fighting them, you realize how big of a powder keg they are, in particular as they can spontaneously re-ignite themselves and water has limited effective (even if still the best we have).

Article on the topic:

https://www.nbcnews.com/business/autos/federal-regulators-wa...

Here's a firefighting training video (start at 3 minutes if it does not):

https://youtu.be/8n5Wf7TlGrU?t=181

Although there are some innovative solutions coming on tap, like this special modified shipping container that you put a still-on-fire EV into and then drive it to another safer location:

https://cfpa-e.eu/container-puts-out-inextinguishable-fires-...

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My guesstimation is that we're just trading modes of failure and it'll roughly be a wash in the end.

Gas cars have leaky oil and combustion happening (my old high school car caught on fire under the hood). Users are regularly handling gasoline at stations.

Electric cars may be a bigger problem parked or at home. Overall less maintenance that might cause a fire but batteries so far seem more susceptible than gas tanks which are dangerous but don't generally ignite. Users are installing charging stations (although should be covered by electrical codes). Fire suppression in the garage and at charging locations might become popular (encouraged by insurance discounts).

Yeah, batteries are "dangerous". We're all still carrying them around in our pockets and purses.

> Gas cars have leaky oil and combustion happening (my old high school car caught on fire under the hood). Users are regularly handling gasoline at stations.

It's worth considering that during the life of the car, far greater time will be spent charging as opposed to time spent fueling one, and even then, a fueling station can easily be outfitted with specialized safety devices that combat fuel fires.

> Yeah, batteries are "dangerous". We're all still carrying them around in our pockets and purses.

Stored energy is dangerous. The higher the density of that energy, the more danger it presents. Vehicle battery packs are designed with integrated cooling, and thus can be far denser than what's in your pocket.

Not to be completely negative, but to expect that there won't be a "safety learning curve" with larger and larger numbers of battery operated vehicles does not seem like sound planning. Met correctly, I'm sure we'll be able to manage it.

>Yeah, batteries are "dangerous". We're all still carrying them around in our pockets and purses.

https://en.wikipedia.org/wiki/UPS_Airlines_Flight_6

"The FAA issued a restriction on the carrying of lithium batteries in bulk on passenger flights"

https://en.wikipedia.org/wiki/Asiana_Airlines_Flight_991

"the International Civil Aviation Organization considered applying new safety standards to air carriage of lithium batteries as a result of this"

I think it'll be a wash too but I think that the failures will move up the socioeconomic ladder so you'll hear more about it.

We could make different trade-offs. If we had electrified freeways (allowing cars to charge while moving), most people wouldn't need large batteries in their cars just for the occasional road trip and manufacturers could use safer, cheaper chemistries like lithium iron phosphate.

This is one reason I'm hoping that lithium iron phosphate batteries catch on for the low-to-medium end EVs that don't need huge range, as the batteries tend to be quite a bit safer. Not that it's impossible to catch LFP cells on fire, it's just harder.

I also wonder if it would help to have an emergency discharge port or something? In other words, a fire truck pulls up and they plug a cable from the car's discharge port that energizes some high-power heating elements to boil water or something. The idea being that the faster you can discharge the battery, the less stored energy you have to deal with catching things on fire again. (Though it might not actually help, since in the short term extracting power from the battery will just cause it to heat up more.)

(The "emergency discharge port" could just be a DC fast charger port with some method to force the contactors to engage.)

Well good news: LFP is likely to become the dominant chemistry in most transport applications that don’t have specific or very high capacity energy weight/volume density requirements, the lower end of EVs and passenger vehicles included. LFPs I expect will slowly eat up the higher end of the market as it specifically improves and scales.

Issues with the discharge port I can see include the issues that:

- broken circuit means energy will struggle to get anywhere even if you wanted. Solving for this increases complexity substantially and non-linearly.

- maximum discharge rate of the cells could mean even at max output it could take well over 10 minutes to depower if not much longer (and discharge also has a trade off of them heating up accordingly at higher discharge rates)

Ultimately, you have a lot of embodied “loose” energy and once the reaction has left your control and the walls of the cell are breached (and enough of them), it’s more akin to a collection of little firecrackers that “combust” when they touch each other rather than a fire that can be “extinguished”. Just in slow motions because they are metals.

...another variation on this would be an emergency water cooling port. Like you have a fixture somewhere on the car that you can connect a hose to and it runs water through coolant channels.

A lot of EV batteries have something like this already, you'd just have the ability to run external water through it instead of just going with a closed loop. You'd also need an outlet, which I guess would spill ethylene glycol all over everything if it wasn't contained, but better that than a burning car.

Many race cars are plumbed with a port that can take pressurized water into the cooling system from the pits, and already have a temp/pressure valve to vent excess pressurized coolant [water in the case of a racecar, coolant mix for a road car] so the tech exists.

I always liked the chemical acronym LiFePO4... it has "life" right in the name!

I’ve been stricken with enthusiasm for hydrogen-powered cars since watching a video from the 90s depicting a backyard solar-powered hydrogen generator which hooks up to a garden hose [1]. It’s supposedly a lot safer than gasoline:

> “These tanks can be shot at with incendiary bullets, or cut in half with a chainsaw, and you could throw a match on them — they’d just smolder like a cigarette. You can’t say that about a gas tank. Here, only the hydrogen you need is released from the tank. When the tank’s heated, it produces hydrogen and the car burns it. So there’s never much gaseous hydrogen in this system at any given time.”

[1]: https://www.youtube.com/watch?v=BX2RxlXCZKA

> When the tank’s heated, it produces hydrogen

The problem is when your garage catches on fire, it heats the tank ...

Still seems to be safer than a gasoline corrolary [1].

[1]: https://hydrogen.wsu.edu/2017/03/17/so-just-how-dangerous-is...

More info: https://www.youtube.com/watch?v=YJBzEYduKK8

Video of electric car starting on fire while charging

https://rumble.com/vjk4qb-electric-car-charging-station-germ...

Isn't oxygen a requirement for combustion ? I've seen usage of blankets to cover cars, this effectively makes it so very little oxygen can go in and continue the fire, why not use that instead ?

Once a battery is in thermal runaway it will keep heating up, oxygen or no oxygen. Putting the battery in an oxygen-low environment would stop the flames but not the heat. You'd still be sat there waiting for the batteries to be done reacting before you can reintroduce oxygen.

Which is why firefighting battery fires is such an irksome thing. You can douse the battery and get the flames out, but hours to even days later the battery can have collected enough heat to reignite spontaneously.

Don't firefighters carry some kind of foam by default? After all there's a lot of grease fires(cars, kitchens) out there.

Foam is not as effective against electrical fires and the manufacturers recommend using water, not foam, on a lithium-ion electric car fire.

According to GM:

> Use copious amounts of water to cool the battery to extinguish the fire

https://www.nfpa.org/-/media/Files/Training/AFV/Emergency-Re...

Foam interrupts the "oxygen" side of the heat-fuel-oxygen fire triangle. Unfortunately, lithium-ion batteries make their own oxygen when heated, so it doesn't help to smother them.

The advice is to use copious amounts of water to cool the batteries, removing the "heat" leg of the triangle. This works but requires extended periods of cooling support due to the possibility of internal shorts re-supplying the heat, and starting the process again.

Maybe we can shoot liquid nitrogen- like in terminator 2 to freeze the battery

Pumping huge amounts of pure nitrogen into the atmosphere sounds like a suffocation risk.

Outdoors?

Fortunately not, and we definitely don't want to increase the amount of PFAS getting into the environment and poisoning our water supplies.

Not usually in the US unless it’s at an Airport. Although larger metros may have specialists. A couple friends of mine are firefighters in a very large city and they will help other counties or cities out with special situations. It all depends on what department has what specialists.

In Germany they often have special nozzles that add some foaming agent to the water to create a water-based foam. They might also have a couple of foam fire extinguishers for cases where you need something that isn't water.

I think the general practice for EVs around here (in larger cities at least) is to extinguish it with water, then put them in a container full of water for 24 hours.

What's done with the water afterwards? I assume it's a large volume of contaminated (in various ways) water?

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