Just use fishpaper. Problem solved
Leave the fiberglass in there. Tape it in place. I initially thought it was also kapton tape in there but regardless you need something more than tape. I never have used fiberglass sheet. I use polycarbonate. I would put more than just fish paper in there and it could take a lot of abuse
Ya, as @Pecos said, your most likely problem is a broken weld in that group. I would pull the group out of the pack and inspect for broken welds. You may then decide to add some welds to the current nickel or replace the nickel if a bunch of welds are broken. Solder it back into the pack once itās at an appropriate SOC and then cycle it watching the repaired groupās behaviour.
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Do you 3d print the polycarbonate? If I can, I think I am going to take an epoxy to stick the cells the the 3d printed polycarbonate. Would it have to be a thermal epoxy though?
Or would it be better to 3d print a part, wrap it in fish paper or kapton tape and then use an epoxy to stick the cells to it?
I get polycarbonate cut at tap plastics here in Cali. Iād tape whatever in place.
Looks ideal
Dang thatās cool
Except have to cut it and itās fiberglass. I hate cuting fiberglass.
Sweet. Sorry for the long chain I just wanna make sure that this thing for sure doesnāt have any issues with contact between cells
Yeah 
This is a more related topic than most donāt be sorry. Cutting that stuff might suck. Getting precut polycarbonate is cheap n easy, at least in cali
Acrylic sheet probably just as good too
3d printing something sounds ideal too. It shouldnāt getting hot enough to melt any of those materials unless u hugely under did the series connection nickel
Trying to save my main 12s9p battery. If anyone can chime in with suggestions, Iād appreciate it.
It sat at ~75% charge all winter. I went to charge it up this spring and when I went back to ride an hour later, the charger kept kicking on for a half second and then stopping. I opened up the pack a bit to get to the bms and all p groups are measuring 3.80v Ā± 0.01v except the last one which is at 4.17. Iām guessing this group is topping off and telling it to cut charge maybe. The p group in question is this guy where the solder bar is laid:
Bottom view
Only thing I can find that looks questionable is this bms lead above. No clue if a wonky lead would cause the issue I described. Bms are black boxes to me and I just wanna fookin ride really fast and offroad again 
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Sounds a hell of a lot like a dead cell or broken weld/s in that group my dude.
Ideally you need to bring that group back into balance with the rest and then monitor what happens when the pack is in use.
If its a dead cell/s or broken weld/s, it would be safe to assume that group would charge/discharge faster than the rest.
If that pack is as old as i think it is, iād say itās had a damn good life and itās day is probably done
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Fuck alrighty then. I appreciate the input.
@Skyart you open to making a 12s8p brick pack? It feels weird knowing you for so long and never having done business before. Your time is up.
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Send it Fam! Dm me
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My Ecomobl pack settled down and got in line. Before opening up to check welds on cell 11 Iām gonna have my bro ride it and charge it back up a few times and see how itās doing.
Before and after
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Have you gone probing at the cells directly with a multimeter, or through the balancing harness? Not sure how destructive it would be to expose them but doesnāt look too bad from the picture.
One question though, that BMS lead pictured is the negative for that group right? If I understood ālast groupā to mean the highest voltage one then it should be. If that wire is wonky, it should be throwing the measurement for the one below it too. If the final lead on the solder bar is wonky, thatād only affect the top group
If you can easily get access to the positive and negative of each cell in that group, you could possibly rule out a bad weld. If they all measure the same voltage, then theyāre all welded together at least enough to look good under the tiny currents the DMM sources or sinks. If one or more of them arenāt at 4.17 then it looks very much like a bad weld.
If they do turn out the same it doesnāt necessarily mean the welds are perfect, you could try and test them under a small current. To me the most sensible way to do that is reconnect the BMS and plug the pack to charge, then measure the cells. When the charger kicks on if one or two of the cells donāt rise in voltage as much as the others, then they have a bad but not completely broken connection to the nickel. If they all rise the same amount, I think thatās a sign of a well-welded but damaged cell (or cells)
Edit: I guess thereās a chance that the pack is completely fine, but the BMS drained every group except the top one?
That big solder blob runs across the top of the last (and questionable) p group. That BMS wire is running to the bottom side of it. I will poke at it later and see if I can measure a bad cell individually in the group.
Got some asshats ripping up and down on my street on gas mini bikes. Wanna race them for slips on a skateboard and watch them cry.
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