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Comment by audunw | Hacker News Reader

Why is it hard to put out a fire when EV batteries are involved? If the fire doesn't start in the EV battery why would the battery catch fire?

It might sound like an odd question, but we have experience with this in Norway, and the results are counterintuitive. Cars in a large airport parking garage caught fire, and it had many EVs in it. Not a single battery pack caught fire. Only the interior of the EVs did. If they were all EVs the fire would likely be less severe, or not have started at all (an ICE car started it)

Battery packs are very well insulated against fires.

Assuming the fire doesn't go completely out of control, I don't see a reason to worry much about battery packs catching fire.

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One of the problems is that lithium ion batteries can't be discharged fully without destroying them. Effectively, the batteries are a very large energy source that can never be fully turned off. Another problem is that (if I understand correctly) lithium ion battery fires tend to produce their own oxygen. Another problem is that a manufacturing defect in one cell could cause the whole pack to catch on fire. According to the article, a fourth problem is that roll-on/roll-off car carriers just store a bunch of cars in one big space, and there aren't barriers to prevent one car from starting all its neighbors on fire.

Putting out an EV battery fire basically entails dumping enormous amounts of water on it to keep the temperature under control until it's cool enough that it doesn't auto-ignite as soon as you stop. That can take hours.

I tend to agree that the risk of EV fires is overblown. ICE cars catch on fire all the time and we don't usually hear about it because it's not all that rare or unusual. It just doesn't make the news. EV fires are a novelty so we hear about them. (Not that any amount of vehicle fires is okay.)

I do think though that if you're moving thousands of cars together on a ship, then that's maybe creating a different kind of risk profile.

I look forward to wider adoption of LFP batteries. They aren't immune to fire; I think the electrolyte is still flammable. They just aren't nearly as energetic when they burn, and they're harder to ignite in the first place.

I'm not sure, but I am starting to think that battery fire is more like nuclear reactor or used fuel cooling than putting out of fire. That is you need to have enough water continuously applied to combat generated heat. Where as with fire just removing heat or oxygen one time is enough.

Yeah, I get the impression that's true. There's an electrochemical reaction that's going to take place whether you want it to or not, and you have to keep adding water until the reaction is finished.

I kind of wonder if it would help to pack batteries with something that requires a huge amount of energy to vaporize, so that the heat from a battery fire just goes into a state transition of some inert substance. (You could boil water off for instance, but maybe there's something more weight-efficient.)

I've heard about large packs on boats catching, sinking, and continuing to burn while wholly submurged, and remote control aircraft being left to burn out because its safer and easier yo just repair the runway afterwards. I'm not sure how you soak that much energy. I've seen metal cabinets where people put iffy packs in case they go. It was clear it had been in a fire at least once. I think the normal way to dispose of such a thing is a controlled burn. Repair is too dangerous, its like defusing an explosive device.

In regards to RC packs, the general consensus is to let them burn out yes. The actual purpose of a "LiPo Safe" or fire safe LiPo storage compartment isn't to protect the batteries from fire, it's to provide a safe space for a battery to burn out completely without burning down your house or car.

> Putting out an EV battery fire basically entails dumping enormous amounts of water on it

That's a problem fire departments are still trying to adapt to, many resorting to putting out the fire conventionally, then submerging the car in a water-filled container.

But I'm unclear on how that makes the risk profile worse for ships? The initial fire should be easier to contain with EVs than with gasoline cars because EV batteries are much better protected than fuel tanks, and water for cooling affected vehicles for a couple hours is plentiful. It's a ship after all.

Maybe there's a discussion to be had about modifications to fire fighting equipment and staffing because of the different demands, but I don't see how the risk is bigger.

> But I'm unclear on how that makes the risk profile worse for ships?

Gasoline-powered vehicles aren't fueled when loaded onto a ship, so they don't really pose much of a fire hazard. However for EVs this is a problem, because it's very difficult to completely drain a lithium battery.

> water for cooling affected vehicles for a couple hours is plentiful. It's a ship after all.

Getting the water to all those vehicles is the hard part. If enough of the EVs catch fire the only realistic way to get that much water to the fire is to get the deck below water level, which tends to be very bad for a ship.

Cars are usually loaded onto a Ro-ro on their own power, and will have some amount of fuel on board. They typically want 10-25% full tanks to account for various contingencies, but I don't know how carefully that's monitored. Given the amount of vehicles in question, probably not that closely, though presumably manufacturers are equipped to be reasonably systematic about fuel fill.

Bilge pumps should be able to keep up with firefighting pumps. But, yes, the firefighting pumps won't be able to handle more than several cars on fire.

Last time I had my car shipped, they checked the fuel level was 1/4 task or less, and made me drive around until it was less than that.

Putting large amounts of salt water in the hold of a ship isn’t something people generally want to do.

"water for cooling affected vehicles for a couple hours is plentiful. It's a ship after all."

Flooding a ship's hold with water is generally regarded as a bad thing.

Indeed, and pouring an arbitrary amount of water into a fully laden ship already has another technical name: Sinking.

Bilge pumps

That's certainly true, but I'm not sure that a car transport ship is designed to quickly submerge a burning car somewhere in the cargo hold until it exhausts its energy source, while staying afloat.

Exactly. The reason is that manufacturers actually go through a lot of trouble to prevent batteries catching fire. They do crash tests, puncture tests, etc. As a consequence, actual battery fires in cars are pretty rare. But they do happen occasionally of course. They are chemical fires so the procedures for dealing with those fires are a bit different than say an ICE car that is on fire. That's all.

In any case. Fire risk on ships is a matter for insurers. There are a lot of EVs that are going to be shipped around in the next decades. And the shipping business is big business. I'm sure they'll figure it out. Lots of ships catching fire would get costly. So, the prudent thing would be to do the math and take appropriate counter measures. But I seriously doubt any insurers are losing much sleep over this incident.

There are also ships that carry the fuel for ICE cars around; or at least the raw ingredients for it (oil). Or liquid gas. Highly flamable stuff. Very toxic. Nasty when it gets out. Oil tankers do untold amounts of damage to the environment when they sink and spill their load. Happens fairly regularly. Insurers are all over that kind of thing as well.

If you actually genuinely care about cars spontaneously combusting, there are hundreds of people that die in ICE car fires every year. ICE car fires are so common that it's one of the most common reasons for fire trucks to be called. Hundreds of thousands of times per year in the US apparently. ICE cars are not safe at all; they never have been. They catch fire in all sorts of situations. In your garage, while they are parked, when you crash them, or when you drive on the motorway. It happens to old cars; it happens to new cars. So, where's the big outrage over good old ICE car fires? There is none. Double standards. Or rather there's a lobby interested in talking about one thing but very much not about the other thing.

Which is of course what is going on here. This article is on a web site aimed at ICE car enthusiast that no doubt depends on advertising, sponsoring, etc. by various car manufacturers. Spreading FUD about EVs whenever they can. Just so the fearful masses keep on buying ICE cars.

If neither the EV batteries, nor high-power wiring energized by them, are actually involved in the fire - then you can* put the fire out normally.

Once the fire actually involves "serious" electricity...well, then you've got (1) "can't blow out" birthday candles from Hell, (2) "spray water on it and you may die by electrocution" issues, and (3) the fire has Unlocked a whole new way to Level Up fast, which does not depend upon the traditional "fire triangle" (fuel, oxygen, and heat).

*Or maybe you can't. Ask any fire fighter whether things get magically easy if there's no electricity involved.

If the battery catches fire they are very hard to out out.

But you are right that it's maybe harder to set the battery on fire in the first place.

It may be harder, but it will happen sometime in the future.

Among many other differences, I imagine cars are packed more densely in a cargo ship than in an airport parking.

Also, the parking did burn down completely. This scenario would be similar to losing a whole ship to the fire, possibly sinking it. Not exactly a good thing, neither economically nor ecologically.

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