[mschuster91]

It's a hack I started doing after a friend's home almost burned down from a vape battery gone bad.

In any case, dry sand is one of the methods firefighters use to put out battery fires, the other being dumping it in a giant vat of water (that's what's done for electric cars) or class D fire extinguishers which are extremely fine powdered salt.

[arghwhat]

Acrylic is itself flammable, massive amounts of sand would be required to fully submerge and cool all cells (and therefore hefty acrylic sheets less likely to give), and it's likely that the sand will not spill correctly and evenly.

Please only use properly designed and tested fire suppression systems, as hack jobs might not help at all and do harm from the false sense of security leading to lack of actually effective mitigations.

[dzhiurgis]

So I need a suppression system to charge my phone now?

[mschuster91]

At least mass-market phones and their batteries by reputable manufacturers go through rigorous testing. The sole exceptions I'm aware of are Samsung's infamous last-ever Note phablets and a few batches of iPhones. Fires of mechanically intact phones are rare.

Shoddy knockoffs and cheap Chinesium garbage however, that's a different thing.

[arghwhat]

When you only have one battery cell it's also hard to screw up battery management, and phone batteries are rarely driven past their prime (no one wants a phone with 50% remaining capacity). The odds are not zero though, as the battery can develop internal shorts from imperfections like dendrite growth over time.

The odds get much worse when you have tens or hundreds of kWh comprised of hundreds or thousands of cells, especially in OPs jank setup with improper battery management and cells that are all already at the end of their life and likely have significant internal damage already.

[hengheng]

Have you burn-in tested this method?