A 12s should charge to 50.4v. Either the charger is faulty or the bms is faulty.
Edit: it very well could be the battery too but the charge and bms are the first places I would look.
Okay, what do I need to change/improve on this pack. Iâm Open to all suggestions/constructive criticismâŚNext build will be a 12s4p P42A
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Fixed on a flexible isolated plate, I think cable ties wonât have a problem. Or should I fix this design with additional Tapes?
Ignore the Green shrink at the Front, itâs not finished yet.
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Bought those cells from Nkon: Samsung INR21700-40T (40T3) 4000mAh - 35A - Reclaimed - 21700 & 20700 - Li-ion - Rechargeable batteries | NKON
And received this:
Almost every cell has bent shell from ripping nickel or copper or whatever was welded.
Cells are for me and friend for personal use, but for big packs(each 100+ cells)
Usually when I got cells like those in my hands, I would use them for vape, flashlight, mini battery pack or just discard them⌠and Nkon sells cells like those! What would you do? Am I too paranoid? Should I return whole order?
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Thats how most reclaimed cells look like. Unless there is a hole in the steel can, just bend them back and use as intended. Nkon guarantees that reclaimed cells are unused (at least they did when I ordered some last time).
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Doesnât get much better than that my dude.
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Aye, this is prime. Iâd set the charge cutoff to 4.15V though.
Edit: Deleted wrong information.
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Any of the standard chemistry li-ion cells we use (not LFP, LiFePO4) are nominally rated to 4.20V and have a max charging voltage rating of 4.25V.
You can get, if not otherwise abused, a bit of longer overall cell life by charging to a lower voltage but charging to 4.20V gives you the full cycle life of the cells.
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Oh then I got something confused, nevermind then.
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OkâŚfinished. Sheâs not pretty but I canât wait to ride herđ. Does it look safe? Iâm planning on opening the enclosure after the test ride to inspect things. Oh yeahâŚI put clear shrink wrap on before I mounted it inside the enclosure.
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In my 12s6p Samsung 30T battery, i get a Pgroup that discharges faster than the others. When charging it also charges faster than the others and finally all get balanced when charged fully.
Maybe a weld in that group has failed? Can i check that with minimum disassembly of the pack?
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Most likely loose nickel on that group, lesser likely is a bad cell. Time to open it up and inspect
If you know the pack layout, count 5 groups from negative and carefully slice the shrink wrap to expose the group. Carefully inspect the nickel may need to pry a haur to find loosies.
Brick pack is easy welding fix, flat pack will be a bit tougher to access welds
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Damn I was afraid of thatâŚI have the same issue with number 4.
I donât think itâs charging faster than the others. The two LLT screen shots are 10-15 mins apart.
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Was just about to give my 18s pack its first charge after seeing the cells are stting at 3.47v. WATE charger from aliexpress.
everything is correctly wired from the charger, to the BMS, i just wanted to double check polarity again from the charger and my charge portâŚ
I plug the charger into the extension bar, and touch the probes with my multimeter which i think read out 74v before popping right in front of me. This actually happened once with no markings when i first got the charger, i thought it was from not switching to 110v on the charger and thought nothing of it. Iâve measured it before like this multiple times with no issues, on the XT30 and on the prongs in the photo.
I got like 2 big pops this time, and my charger is cooked⌠already ordered another LP20 connector, but why did this happen⌠next time do i just wire it up and not check it with my meter??
1 is positive, 2 is negative
I suspect this might have something to do with it.
I like to use an xt connector on my chargers and then make adaptors. Xt connectors are much safer to check polarity on
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this LP20 is hooked up via xt30 as the charger came with one already soldered on
Didnt realize that metal would cause issues as i probably bumped it while trying to steadily touch the probes and move my head to read the meter
Oof. Next time check it at the xt connector
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Looks like you shorted the meter probes to the metal shell. Donât do that, it causes sparks and can kill your charger.
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Itâll also kill your probes, my positive is now a few mm shorter. 
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