Lithium battery fires

[David Paste]

They provide their own fuel and oxygen from what I understand, and are near-enough impossible to put out.

What about dumping dry ice on them to cool the fire out?

[John Rumm]

Not impossible - but more difficult. It does depend on how much lithium is present in the battery - it is only one component of it, not a pure lump of metal.

In some cases you can use *lots* of water, but there are hand held fire extinguishers designed for the purpose that are better for smaller fires.

[Colin Bignell]

You would need massive refrigerated vehicles to carry enough dry ice.

There is a pancake nozzle, designed to be slid under the battery, so that it can be cooled with lots and lots of water, but the construction and position of the batteries limits its effectiveness.

The consensus seems to be that the best approach to a vehicle battery fire is simply to let it burn itself out, which will usually take about an hour, while trying to prevent the fire from spreading.

[David Paste]

Thanks John. I was just thinking about it after the fall-out of this Luton Airport fire. If an electric car was on fire, could a fire engine full of dry ice pellets turn up to cool it out. Nothing more complicated than that :)

[David Paste]

I did wonder how much would be needed! Thanks Colin.

[Clive Arthur]

Trouble is, apparently Lithium metal will burn in CO2 - it rips the Oxygen out (technical term). Whether that's enough to overcome the cooling effect of frozen CO2 I don't know.

I was taught that Sodium Carbonate or Bicarbonate was the best thing to use, but that was for small batteries, not vehicle sized.

[Tim Streater]

And it burns in water, too. As do sodium and potassium.

[Theo]

Where would the dry ice come from? Would they need a freezer trailer plugged in 24/7 to be ready? It's not like a pump tender where they can pump it from a hydrant or the nearest lake.

Also you'll suffocate anybody in the vicinity, so they better be wearing breathing apparatus. You can't do it if there are civilians in the area.

[The Natural Philosopher]

Trouble is, it isn't the lithium that burns. It is not present in metal form but as a salt, which doesn't burn.

What burns is the electrolyte Which releases oxygen all by itself. So no method of depriving it of oxygen is going to work

[Paul]

I have seen a claim that I do not believe.

Some company has done the research and claims that if the failing battery pack is shoved into liquid nitrogen, the runaway behavior will stop.

Now comes the interesting part.

They claim that if you drop a battery pack into liquid nitrogen, the pack will function properly later. And have a normal lifespan. In other words, if you recycled a failed pack, disconnected the cells, you could reuse the cells in another pack.

And I don't buy that.

So yes, dry ice is an idea, but someone has actually done the research using liquid nitrogen as the ingredient.

The reason for using a fluid, is for enhanced heat transfer. If the pack emits X amount of heat, and you need to remove all that heat, plus cool the pack further, then liquid nitrogen is going to do that faster. Being a liquid, it conforms to the surface (once in a while).

If you have some experience with this, the violent evolution of gas can prevent liquid contact, or reduce the percentage of time the liquid touches. And this is how some people do stunts with open dewars (stunts I would not try). I've only had some minor skin burns from tiny splashes of liquid nitrogen on the skin, and that teaches you enough, to be more careful the next time.

The article did not explain what temperature distribution was achieved on a runaway pack, when attacked that way.

I can just imagine a fire truck now with 5000 gallons of liquid nitrogen in it :-) "Who wants to hold this hose for me?" The article I was reading, had no details at all, as to how a fireman delivers and dispenses this solution.

Paul

[Paul]

... And this is why they are working in the lab, on solid electrolyte batteries.

There is, of course, a hype-wagon pulling this tech around. Claims, and counter-claims.

"Numerous automakers have announced that EVs with solid-state batteries will arrive in some form around 2025, with more on the way by 2030. Some automakers are developing their own solid-state technology, while others are working with partners, including start-ups and established companies. Some automakers and their partners are taking things a step further, forming entirely new joint ventures to get solid-state batteries into production EVs."

"Research conducted in 2021 proved that solid-state batteries could recharge and discharge at least 10,000 times" <=== recharge inside the stock prospectus folder... the other number I saw was "1000" "Real hurdles remain for solid-state batteries to overcome...

...and a new generation of EVs is coming."

*******

"Can solid-state batteries burn?"

https://ts2.space/en/can-solid-state-batteries-burn/ "The truth is that while solid-state batteries are generally considered safer than their liquid electrolyte counterparts, they are not entirely immune to the risk of fire.

Although the solid electrolyte is non-flammable, other components within the battery, such as the electrodes and the separator, can still catch fire if exposed to extreme conditions."

But during a puncture event, that would presumably be a different kind of fire, with a different degree of energy extraction. The heat to keep the fire going, would be the arc-welding type of heat. Could a BMS stop that ? Could a thermal breaker, break some connection ?

Paul

[Clive Arthur]

<snip>

And then there's the problem of people quite happily dying of anoxia without realising they're breathing nitrogen.

[Colin Bignell]

As the fire will be producing toxic fumes, it is usual to evacuate everybody except firemen wearing breathing apparatus from the area.

[Paul]

What I thought was odd, is who gives a rats ass whether the pack is affected by the LN2 ?

It seemed to be a statement to the insurance industry.

Ordinary people want to know whether you can stop the fire, and cleanup afterwards is a minor problem.

Paul

[Colin Bignell]

On 14/10/2023 02:16, Paul wrote: ..

Thinking further on this, liquid nitrogen might work with injector nozzles. Those have been designed to be fired into the battery pack, usually remotely, so that water can be fed to the interior in the hope of cooling it down. Using liquid nitrogen instead of water should both be more effective at cooling and avoid the problems of injecting a conductive liquid into the battery pack.

It would need a new type of appliance, specifically designed to fight car battery fires that carried the liquid nitrogen, possibly in an ISO cryogenic shipping tank, which could quickly be swapped out at its base, and a robot to fire the nozzle into the battery pack, but that might be justified in a large city.

[Theo]

Won't the liquid nitrogen boil rapidly? Not just causing an explosion of the pack (which may or may not be helpful in terms of controlling the fire) but provide a lot of pressure which pushes against attempts to inject more liquid nitrogen into it.

Injected water will boil rapidly too, but it boils at 100C not -200C.

Specific heat capacity of water at 25C: 4.2 kJ per kg per K Specific heat of steam at 100C: 2 kJ per kg per K Latent heat of vaporisation: 2256 kJ per kg at 100C (=0.63kWh per kg)

Specific heat capacity of LN2: 2 kJ per kg per K Latent heat of vaporisation: 200 kJ per kg at -195C

Assuming both are heated enough to boil:

Taking the LN2 from -250C to 150C:

2*400 + 200 = 1000 kJ absorbed

Taking the water from 10C to 150C:

4.2*90 + 2*50 + 2256 = 2734 kJ absorbed

So the water has almost 3x the cooling capacity than the LN2, and is a lot easier to deal with.

Theo (anyone care to check my assumptions?)

[Colin Bignell]

One of the problems I read about with the water injection nozzles is that they dump a lot of water into the surrounding area; far more than would be required for fighting a normal fire. So, while boiling the water is certainly an effective way to remove heat, the main mechanism seems to be using water to transport heat away from the battery. It also implies that they vent excess water to atmosphere, which should prevent any build up of pressure inside the battery case.

[Sysadmin]

The successful quenching of the Windscale B2 reactor fire in 1957 was with water.

[Colin Bignell]

I think turning off the fans that were feeding air to the fire also played an important part.

[Paul]

To stop the fire source in a lithium pack, you have to get all the cells cold enough, to that they stop with the runaway behavior. They emit heat that can restart a fire.

Individual cells may have a thermal fuse, which could stop the entire 800V circuit. But if there are puncture wounds to cells, those cells might still be able to emit heat later, as they discharge.

If the only thing "driving" a cell, is heat from the fire, then dousing in liquid nitrogen is going to work.

But if the source of the energy is multiple puncture wounds, then the liquid nitrogen stops the "bystander" behavior, but cannot help drain the punctured cells so that they can no longer heat the surroundings. After the application of liquid nitrogen, maybe the scene needs to be viewed with an IR camera, to spot which parts of the pack are still excessively active.

I don't know if there is any requirement for the battery pack to be "easily removable by fire personnel". Dunking the entire assembly in a very large dewer, that might be difficult to arrange. Injection sounds fine in principle, except for cases where there is still thermal emission later.

Paul