No worries. It survived. I still use it. 
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Did you ever track down the specific cause of the overtemp cell that led to fire?
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Unfortunately not. It’s a mystery. The only hint I have is that the Unity connector desoldered itself.
So probably something shorted out around there.
Now that I think about it, it would have been worthwhile checking the continuity between the two desoldered lead.
Here’s how everything looked inside the enclosure before the accident.
I had an XT90 parallel adapter for connecting an external battery.
Maybe something went wrong around the parallel adapter. It’s really strange though. I have done all the soldering myself and I believe my soldering skills are pretty decent.
Also, I have used this for a few hundred km both with and without the external battery before the accident happened.
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MMMMMMmmmm Well, in case of fire…
Run to the hills…Run for your life…
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hmm, what if you integrated dry gunpowder into the deck and when it catches fire, it detaches the battery part from the rest of the deck? 
#buildingforfailure
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That’s an interesting idea. I’d love to see something like an over or under-discharge cutoff sensor built into the voltage meter that most VESC’s have.
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Did you have any kind of padding around the pack? From my perspective it looks like the pack was rubbing against the rough interior of your enclosure. It’s hard to tell without being able to see the battery construction itself but it looks misshapened.
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There was no padding but I don’t think this was the problem. For the rubbing to happen the pack would have to move inside the enclosure which it didn’t because it was taped to the enclosure with a strong double-sided tape. When I occasionally needed to remove the pack from the enclosure for servicing, it always required a lot of force. Also, if there was any rubbing, that would cause damage to the shrink wrap and there wasn’t any.
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I’m late to this party but there’s no metallic lithium in a rechargeable li-ion cell to react with anything. Only non-rechargeable lithium-metal cells have actual lithium metal in them.
You’re right about the extinguisher. The very high temperature exothermic reactions that are running wild in a cell that is in thermal runaway make putting out a battery fire very hard to do. The cathode material supplies oxygen and both the plastic separator sheet and the flammable electrolyte liquid supply fuel for the fire.
The best way to stop a li-ion fire is with water or an aqueous fire-fighting solution. This can quickly lower the temperature of the cell(s) below the thermal runaway threshold, keeping the fire from restarting once you put it out. Then it’s a simple matter of just putting out the fire from the burning plastic and organic solvents with more water or an extinguisher.
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Vibration does funny things. It absolutely can have abrasive action happening even though it appears to not be moving. The moving can be very slight, micrometers, but still abrade.
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maybe the cells were overcharged?
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Firemen just dump a s### ton of water on it the more the better
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I kind of agree and kind of feel like designing for failure is a bad idea.
Designs should incorporate fire prevention, not fire suppression.
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If you want to reduce a 3rd of you batery go for it. That’s how mutch space is wasted by the case reinforcement and slide system. Personally I make my battery’s as small as possible with the desire discharge ratting and I can barley make them fit
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