[arghwhat]

If the batteries catch fire the acrylic bottom will melt and automatically dump the sand onto the fire.

This is a questionable setup though. You'd need massive amounts of sand dumped evenly, which requires more design and verification. Acrylic is also itself flammable.

A basic water based fire suppressor would not extinguish a battery fire but it will cool it and the room, limiting spread.

Let the experts design this kind of thing.

[mschuster91]

> A basic water based fire suppressor would not extinguish a battery fire but it will cool it and the room, limiting spread.

That's the thing: it will not, quite the contrary - unless it's many tons of water at once that quench the fire, the burning lithium will just go and create hydrogen gas that in turn recombines and leads to an even larger fire.

[arghwhat]

I think you're confusing suppresing the fire and extinguishing it. You are not trying to stop battery cells that are currently on fire from burning - you will just have to wait for those to be out of fuel. The purpose of fire suppression is to stop new things from heating up by the fire past the point of combustion, catching fire and thereby spreading it - be it more battery cells, construction materials, you name it.

Modern EV fire suppression systems for parking garages use high pressure water mists to contain the fire to a single vechicle for example. This keeps neighboring cars cool and avoids them catching fire, and cooling down the burning vehicle may avoid spread to more battery banks or other flammable materials.

[mschuster91]

> Modern EV fire suppression systems for parking garages use high pressure water mists to contain the fire to a single vechicle for example.

Indeed but look at the size of the pipes and the pressure they're operating at. Far above the typical residential, what, three bars that come from the utility. The volume of water is the key.

[arghwhat]

Your home residential battery is not an entire parking garage full of EVs, so looking at their pipes and pressures is not relevant.

Those pipes are dimensioned to be able to suppress fire in every parking booth of an entire parking garage full of EVs, each of which packing more of a punch than most residential battery installations. While it cannot handle every car being on fire, it needs to handle any car being on fire when it goes off.

This is orders of magnitude more powerful than what you need for a small residential setup. Have a professional evaluate what system is best - if they suggest a sprinkler system, which they might, I am sure they would understand the capacity of your residential water supply and suggest upgrades (new piping to mains or buffer tanks) as needed.

[mschuster91]

Fair point. The problem is, the cost for such a consultation will run into the five figures, that's more than even a brand new battery pack setup from a reputable brand costs.

[arghwhat]

I don't see how a short consultation on the matter would exceed 3-4 digits. It's maybe an hour from a specialist to see what is needed. Saving your bacon later on is worth some cost.

Worst case, you might also have existing recommendations or fire code/regulations for battery energy storage systems in your area, and while those specifically may be overkill they give an idea of what is considered necessary. Maybe you could consult your local fire department, depending on how things work in your area.

[Etheryte]

Do not use water to try and put out a battery fire. It's not as bad as throwing water on burning oil, but it's not far from it.

[arghwhat]

Battery fire suppression systems often use water, and firefighters will also certainly apply water. Just don't walk up to the cell with a bucket of water.

Water can and is used to cool batteries during battery fires, and more importantly, to cool the surroundings so that the fire cannot spread to, say, neighboring banks/cells or construction materials. Modern EV fire suppression systems for parking garages use high-pressure water mists to avoid the fire spreading to neighboring vehicles for example.

The recommendation about oil and water focuses on a larger container of liquid fuel that is on fire at the surface and heated far past the boiling point of water, such that dumping a large volume of water onto it all at once causes it to immediately boil and explode, spreading large amounts of oil as a mist in the air, which both spreads the fire and causes a much more violent combustion. A water-based fire suppression system (not a guy with a bucket of water), or a firefighter with a water hose, can absolutely extinguish such a fire.

Hacking together a sand container of acrylic may well do nothing to limit the fire while simultanously giving it more fuel (acrylic) and pathways to spread to (whatever the acrylic is near).

The point is: Don't hack together a fire suppression system, leave that to an expert please.