Beginners Guide to Processing 18650 Cells | Cell Database


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Fine dry sand as a fail-safe smothering agent for battery fires
#1
I haven't really been considering stationary lithium batteries much until just lately but the idea came to me a few years ago when building ebike batteries to use fine dry sand held back by a plastic dam or  dams arranged so that  if the dam or dams melt the sand floods the battery space. I don't think I've seen the idea anywhere else and this seems like the ideal forum to share it on.

That's about it, choice of plastic, thickness and configuration of the dams, arrangement of the sand reservoir, the battery space and so on to be determined.

I've seen a small lithium battery fire, a big one could be catastrophic, I'm sure thinking about doing this with my upcoming setup.
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#2
That would be interesting. Not sure how practical it would be, but it could be a possibility. I haven't looked into how the batteries react with water, or other types of retardants. Something worth looking up, though.

Questions to think about would be:
1) How hot does the liion get when on fire?
2) How hot does sand get to melt?
3) Could sand that has reached the temperature of an inflamed liion possibly ignite others?
4) What type of sand would be best to use?
5) What other types of materials could be used that could be easily cleaned up?
6) Add future questions here..... :p

But I do like the idea of being able to snuff out any kind of fires that may start within the confines of flammable building.
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#3
Silica sand is quartz granules, quartz is very stable and has a melting point of 1670C. Silica sand can be purchased as blasting media in various grades down to near-talcum powder consistency.

I did come up with a potential dam material, nitrocellulose cloth. It's possible to treat ordinary cellulose cotton cloth such as a tee shirt in order to make it into extremely flammable nitrocellulose but still mechanically almost identical to regular cotton cloth. There wouldn't be any melting with that stuff, one touch of a spark and it's gone in a moment and in comes the sand.

I lived near the beach for a few years in the days of my youth, we used to build fires in the dunes at night and a sure way to smother even the hottest campfire was to shovel sugar sand on it. That's what got me thinking about using sand as smothering agent for battery fires.
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#4
I had the idea of putting a pane of toughened glass between the cell compartment and whatever fire suppression material chamber.
Didn't think of using sand, I was going to use water as last defence measure.

Toughened glass, is pretty likely to shatter into a thousand pieces when subjected to uneven heat, shock, physical impact. Thus dumping the entire load of sand in at once.
I'd probably chose a coarser sand, as it's less prone to being blown around by cells venting etc.
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#5
No water on burning cells thank you Smile If you havent seen lithium react to water before on chemistry Big Grin

https://www.quora.com/What-is-the-best-w...nic-device

Not sure how the fact on above is but i read the main points and they are pretty accurate.

Sand or Salt is the answer.
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#6
Dumping sand on my pack would create a work of art I think... Imagine an archaeologist in a million years that digs up 4000 18650 cells encased in glass.
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#7
I think I have come up with a truly shade tree way of doing this, plastic freezer bags full of sand on top of each bank of cells.

(02-22-2017, 09:59 PM)station240 Wrote: I'd probably chose a coarser sand, as it's less prone to being blown around by cells venting etc.

I thought about the granularity of the sand as well, coarse enough to be a better insulator due to lack of contact between grains and air space but not so coarse to allow enough air to get to the cells to continue the reaction.
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#8
The air itself does not do much to the cells. Lithium can burn in water as well where there are no "free" O2 molecules... (I hope i remember my chemistry correct now)

The problem with Lithium is that it do have all stuff needed to actually burn. Or at least kind of. And that makes it very very hard to stop burning.
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#9
I've seen lipo burn underwater, I'm sure 18650 will do the same. As I recall lithium is so reactive and the flame so hot it strips the oxygen from the hydrogen atoms in water.

I looked around and found a box of culled cells that haven't gone back to the recycle, I'm going to try a zip lock bag of sand on top of a few after I ignite them with a torch and see what happens.

As someone I know is fond of saying "One test is worth a thousand opinions."
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#10
Same here Smile I did some burn tests the other day and that video is coming up today.

I also have some 100 cells more that i could fire of if needed Smile
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