[Syonyk]

They're an absolute pain in the rear to deal with, because they're self igniting, and it propagates between cells.

Your typical lithium 18650 - vape cell, old laptop cell, whatever you know it as (18mm diameter, 65mm length, cylindrical), has a high end capacity of around 3500mAh - so 3.5Ah (amp-hours - so will take an hour to drain at 3.5 amps, 3.5 hours to drain at 1 amp, handwave goes here). At 3.7V nominal, that's around 13 Wh (watt-hours, a measure of energy capacity).

As a first order handwave, when a cell runs away and burns off all the materials in it (electrolyte, plastic separators, etc), you'll get about twice the energy out of the cell as the electrical capacity - so, ballpark, 25Wh for a fully charged 18650 running away. Except, it doesn't run away in an hour. It runs away in about 30 seconds, so doing the math on that, you end up with about 3000 watts for those 30 seconds. That, meanwhile, can heat nearby cells up enough to cause them to enter thermal runaway, and the whole pack will just go, until cooled sufficiently.

"Dumping a lot of water on the pack" will, generally, cool it down enough to stop this. Assuming you can get the water where it needs to be, and in something like a shipping container battery, that's far from given.

At this point, you've got a damaged battery, in unknown condition, with none of the existing current paths able to be relied on, and probably new current paths that may or may not exist yet (water, metal, corrosion, and those paths are often high resistance and slow to form, which creates a lot of heat). It's not really safe to disassemble it or work on it until things have been discharged, because if the pack has energy left in it, it's prone to do exactly what this article talks about - reignite, later, inconveniently.

As far as disassembling it, would you go work in a few megawatt-hours of energy, in unknown configuration, with the state of the safety systems unknown, in a charred environment of unknown toxins (what you get out of a runaway is far from predictable, beyond "generally unfriendly to humans")?

It sounds silly, but if the pack is confined and the fire isn't going to spread to other packs nearby (which is why they tend to be quite spread out), the safest thing to do really is to let it burn to completion. At that point, if it's actually burned out, there's no energy left in the cells to do anything terribly nasty, and you've burned off most of the electrolyte and such.

Anyway, the right answer is lithium iron phosphate for grid scale energy storage, but even those can catch fire if water gets in the wrong places, and they will, with enough prodding, burn.

[rtkwe]

Yeah I get they're a complete nightmare to deal with because they're self oxidizing it just feels like we should have a better solution post fire than letting it sit and hope it doesn't reignite since they're so important and wide spread in our world.