this post was submitted on 30 Aug 2024
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Ok a few things:
Batteries don’t need “a few sparks” to catch fire. They will generate plenty of heat if punctured and self-ignite.
You don’t pour water on a grease fire because grease floats and it will spill out of your pot and catch the rest of your kitchen on fire. Also the water will boil and splatter oil everywhere.
Also pouring water on a battery fire is the preferred way to put it out. Many of the chemicals in the battery will release oxygen when heated, so the best way to put it out is to cool it down as much as possible by dousing it with a shitload of water. It isn’t always possible to apply enough water to the core of the fire which is why they are hard to put out. Sand won’t do anything because the fire is self-oxidizing.
Yes lithium metal reacts with water, but that’s not what makes batteries hard to put out.
I worked at a lithium ion battery company for 11 years. Water won't do it. When ruptured, a lithium ion battery goes into something called thermal runaway. You need to use CO2 fire extinguishers to cool the batteries to get the fire to stop. Otherwise, it will burn until all the energy is used up. I suppose it's possible to use water that's cold enough to stop the reaction, but I highly doubt it.
Water turning into steam soaks up an enormous amount of heat. I assume that thermal runaway happens somewhere above 100C, right?
CO2 extinguishers work by displacing oxygen, not by cooling.
The rapidly expanding co2 does get very cold though. It’s not any different from freezing things with compressed air cans.
I don’t hover, know which would absorb more heat per pound though. Someone who knows more math than I can do it though.
If I’m reading Wikipedia correctly, it takes 348 Joules of heat to boil a gram of CO2.
Water is 2257 Joules per gram. As long as you don’t need anything cooled under 100C, water is the way to go for cooling. It’s also a hell of a lot cheaper and easier to deal with than liquid CO2.