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Thermal Runaway on Purpose
#11
This happened to my ebike battery over the summer during testing. Totally operator error, the bottom of the battery was hitting the water bottle holder screws I didn't take out of the bottom tube. I only noticed after my range went way down. These are 3.2ah 10a ncr18650db's (same tesla uses). Nothing catastrophic surprisingly. I was able to manually balance the packs then replace the damaged ones. Probably have like 150 cycles on it since then.  

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#12
It's amazing that there was no fire, considering the number of cells that are in parallel on that pack! Perhaps the bike frame was steel and had too much resistance to pass enough current to start a fire?
Check out my long-term capacity test of 18650s: https://secondlifestorage.com/showthread.php?tid=6868
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#13
I have accidentally (well rather, out of lack of basic safety calculation) caused a cell to go internal short, and go into thermal runaway. Luckily nothing too bad happened, I was able to submerge it in ice water until it drained itself out. Still a very scary experience, and one I wasn't really prepared for.



2:02 is just before the cell goes internal short (you can see the pack voltage drop from 26.5V to 22.9V). This was after 2 pack dead-shorts while trying to test the protection functionality of a BMS. There's more info on the slide at 19s in the video. The cell is an LG F1L (as far as I can tell with my visual and electrical test methods), though may not be a legitimate or "grade A" cell, since it was a rewrap from China.
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#14
You got lucky, that thing was really hissing! Looks like the CID popped too late. But the fact that you could hold it in your hand makes me think something else happened. When I accidentally shorted a high drain Samsung cell, that thing got up over 235*F/112*C, but it didn't hiss and CID protected it from getting worse. How hot did it feel in your hand?
Check out my long-term capacity test of 18650s: https://secondlifestorage.com/showthread.php?tid=6868
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#15
(02-07-2020, 04:33 AM)Generic Wrote: You got lucky, that thing was really hissing! Looks like the CID popped too late. But the fact that you could hold it in your hand makes me think something else happened. When I accidentally shorted a high drain Samsung cell, that thing got up over 235*F/112*C, but it didn't hiss and CID protected it from getting worse. How hot did it feel in your hand?

The body of the cell was not too hot, probably less than 60C which is about the tolerable threshold for holding. The short was definitely localized in the top cap of the cell. In retrospect I should have put the thermal cam on it, I forget if I had it at the time.
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#16
In that situation, you are only thinking about your own safety and about protecting the property around you from damage, should the cell explode or flare up. The last thing on your mind is "hey, is my thermal camera around?" Luckily I was filming the whole thing, so I was able to go back and see what exactly happened. As soon as I saw the puff of smoke, I got the pack I was working on outside and away from anything flamable, and that's when I noticed the cell was hot. Grabbed my cheap infrared thermometer and noted the temperature. Then I got my leaf blower and blew on that thing for at least 5 minutes straight.
Check out my long-term capacity test of 18650s: https://secondlifestorage.com/showthread.php?tid=6868
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#17
(02-07-2020, 04:33 AM)Generic Wrote: You got lucky, that thing was really hissing! Looks like the CID popped too late. But the fact that you could hold it in your hand makes me think something else happened. When I accidentally shorted a high drain Samsung cell, that thing got up over 235*F/112*C, but it didn't hiss and CID protected it from getting worse. How hot did it feel in your hand?

When I accidentally shorted a Samsung 13q the fuse burned and nothing bad happened.
I removed its cap and making a contact directly to the internal + worked, the cell was still usable.
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