Beginners Guide to Processing 18650 Cells | Cell Database


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Fine dry sand as a fail-safe smothering agent for battery fires
#11
Elmo: If you dont mind i have an idea to test as well if im allowed to put up a video of that? (I ask since you came with the idea first... )

Thats how I am Smile
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#12
Daromer, I'd be thrilled to see a video of your test, please by all means be my guest. I don't watch many videos because of bandwidth limitations on my connection but I'll make it a point to watch that.

I'm a big fan of fail-safe, if it can be done for DIY Powerwall packs as cheaply and easily as I suspect it might then it would be immoral of me not to share a potentially life and property saving idea.

A bag or bags on top of the individual packs keeps potential cleanup to only the one pack with a little forethought in the design to isolate the packs. Orient the cells vertically and each one will be the same relatively short distance from the plastic and the sand.

Does a sand-quenched pack require fuses? I admit I built 12s12p ebike packs from harvested cells without fuses before I knew better but nothing ever happened to them in quite a few thousand road miles. I kind of shudder to think of the meltdown I could have had between my legs. Talk about a hot time in the old town tonight...
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#13
(02-23-2017, 08:40 AM)daromer Wrote: 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.

(02-23-2017, 08:55 AM)Elmo Wrote: As I recall lithium is so reactive and the flame so hot it strips the oxygen from the hydrogen atoms in water.

Sigh, I see I have to have this discussion here too.
The fire comes from the unstable electrolyte (Ethylene carbonate) reacting with the positive anode (Cobalt Oxide, CoO2).
So you have fuel and oxygen created, hence the mini rocket nozzle.
The lithium is in the form of a compound, and in small quantities, so has minimal involvement in the chaos above.

See this page for a detailed breakdown of the chemical reactions within a failing Lithium Cobalt cell.
http://www.mpoweruk.com/lithium_failures.htm
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#14
We all have our areas of expertise and interests, electronics more so than chemistry happens to be mine. Lithium metal will in fact burn underwater by the process I mentioned, that may not be what is happening in a burning 18650 cell but it can and does happen.

It's difficult to get all the caveats and details into a brief forum post, I do know that lithium cells contain sufficient products for combustion on their own, I assume that extra added oxygen will not help matters when trying to extinguish such a conflagration.
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#15
Station240 Thanks for correcting Smile
Was unsure there what parts was involved. Only remembered that when they go they go.

Elmo i will do a test to see. I have an idea i want to test.
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Current: 10kW Mpp Hybrid | 4kW PIP4048 | 2x PCM60x | 83kWh LiFePo4 | 10kWh 14s 18650 |  66*260W Poly
Upcomming: 14S 18650~30kWh | Automatic trip breakers, and alot more
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#16
Anxiously waits
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#17
In the meantime, let us enjoy some slo mo explosions:



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#18
I wonder how much sand would be required to snuff a fire before it got out of control? Think house fire and tossing a kid's sippy cup worth of water on it.  You'll get a bit of steam but won't do anything else.  Dump a water bomber's worth of water, it might flatten your house but it would likely put the fire out right away.  Challenge is finding the happy medium.

I know if you look up fire extinguishers for lithium fires they always talk about type D instead of the more common ABC type we should all keep around the house.
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#19
[Image: kzxXt4.jpg]
This is my idea.

You have 2 boxes on top of each other. The bottom one will be the one with batteries inside. The top one holds the sand. Only thing between them is chicken net and the plastic. 
Chicken net is there to keep the plastic from fall down and keep the sand up. And the plastic holds the sand. As soon as any fire comes the plastic will melt and let the sand fall through down on top of the batteries....

Lets see if i get some hours free this weekend to test it. And if you got any sugestions let me know.
My plan is to heat the batteries with a heating element placed under the batteries.
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Current: 10kW Mpp Hybrid | 4kW PIP4048 | 2x PCM60x | 83kWh LiFePo4 | 10kWh 14s 18650 |  66*260W Poly
Upcomming: 14S 18650~30kWh | Automatic trip breakers, and alot more
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#20
Now, I'm assuming that the packs would 'have' to have the positive side up, correct? That's the end with the vent holes and the designed end to fail under super-violent discharge.

This idea wouldn't really work for a lot of us who plan on or have our packs hanging end-to-end, like Pete's. Wonder what other idea could be use for snuffing out hanging packs. *ponders*
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