I’m over here gluing my cells got resin on my p45b’s right now I’m just curing my shit I’m high voltage as fuck man I’m a freak man like
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Thank you so much @BenjaminF I appreciate the time put aside to write these out.
And thank you @xsynatic for the good meme 
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Always happy to help someone who’s willing to learn!
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Have you learned what voltage cells can get down to and still be revived?
@jack.luis
@xsynatic
I’m still waiting to hear what I wouldn’t listen to from …”the experts”
@BenjaminF oo if only I could get some of that helpful advice. Seems I’m not willing to learn. I do t know what I’m not willing to learn though and they can’t say. Say it all
Are you still using the Cyboard btw?
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Nah it’s been thoroughly gutted for parts. All that’s left now is the deck. I have low priority plans to turn it into a coffee table you really don’t wanna run your shin into.
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LiPo C-ratings are useless, marketing-driven junk that offer nothing. They are spectacularly exaggerated by most hobbyist LiPo pack assemblers.
The ultra-high capacity “standard li-ion” round cells often use c-ratings for some things and those are pretty accurate though since it’s the big cell manufacturers setting the ratings.
There’s no way for you to confirm a pack’s C-rating except by testing it or looking for someone else’s test results. A C-rating that is higher than the fusing current (melting current) value of the pack’s wire leads is a good indication that the rating is BS though.
For example, a 5Ah pack rated 60C (300A) with 12AWG wiring that literally melts after a few seconds above about 230A.
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Everyone get back to my literally unexplainable issue that started this mess 
My cell 1 goes high, 5 low, 10 low sometimes and only when connecting the charger. All balance wires connected properly.
Don’t get distracted, I need input lol
It is a general battery thread ya’ know.
There’s not much we can do here. You can try…
…another charger and see if the behavior changes. If it does then buy another charger.
…another BMS. If the problem goes away then toss the old BMS.
…replacing the balancing harness.
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Haha yes I know… I just came here with an actual concern and it derails completely
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Fine John, I’ll take the bait again
First the genuine answer:
Can you try measuring the voltage on the BMS headers specifically while the BMS is reading wonky voltages. I saw that you already thought of measuring at the header, don’t worry I know you thought of that basic approach. But specifically, can you try with a fast-reading DMM set to PEAK or HOLD. Leave this connected for as long as needed to get a couple of reading pairs - both a BMS and DMM reading from the same instant. If you have an oscilloscope you can set to single shot trigger that would be even better.
When the BMS is reporting high+low voltages, if you can repeatably show that the DMM disagrees, then you’re probably correct that the balance leads are fine. The aim is to isolate the error as much as possible. I know you measured the voltage already, but it’s clearly an intermittent fault, so you need to catch it while the BMS is also reporting the fault
Secondly:
The reason no one is offering new specific advice is because they already offered advice. The very first response offered you a simple, good faith suggestion
I’ve now expanded on the suggestion to clarify why there is more you need to do to draw a conclusion. Take this advice, or decide you’re satisfied that we’re wrong and you need to buy a new BMS. Either way, we’ve now made it exceptionally clear that no one has more advice to offer, so stop demanding we give more
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To me, this sounds like a bad connection in the pack. When no current is flowing, the voltage reads fine. When current is flowing, the high resistance of the bad connection causes huge voltage drop, and that explains your weird readings.
I would be investigating all of your solder joints, any spots where the thin balance wires might have pinched or frayed, and the solder connection of the BMS wires (B- and C-).
Maybe once we fully colonize mars humanity could maybe come up with a way for a BMS to know the difference between a cell actually at 10V or a broken balance lead
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It already exists.
Any BMS I design has open balance lead detection which triggers the BMS protection circuitry (varies based on BMS requirements). This is completely independent of the cell overvoltage detection (and protection).
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Good. Thank you.
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I would agree, only thing this does not happen when I put the battery under load. Then there’s perfect uniformity of the voltage sag.
Shaking the whole thing and or jiggling all cables around made absolute zero difference.
I’m still quite set on it being the fuse holder that had bad connection (on the + charge cable). But I can’t come to any reasonable conclusion how that would give me suddenly 2.2 A charging and strange cell values VS 1.8 A charging and fine cell values (in the app I didn’t have any measurement tools oscilloscope or whatever at hand). Possibly the charger goes crazy and messes with the BMS somehow.
Been away for a a day or two now. I’m gonna put a different fuse holder and fuse when I get back home and see if it ever comes back.
I really love those PCB’s. Truly a pleasure to build on.
Need one for Onewheel and I’d be stoked 
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Rest easy, sweet prince. RIP. Next time I’ll try not to leave you on (and maybe install a loop key to be sure)
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I have a 12v Lead acid battery charger that that i learned not to trust to not overvolt.
I installed an inline wattmeter on the DC outputs to monitor its insane behavior, and the voltage and amperage figures started jumping all over the place, but same exact wattmeter was rock steady and accurate on other battery chargers.
I tried a snap on ferrite on the DC output ground cable, and as soon as I started closing the locking snaps, it started buzzing loudly, and vibrating in my hand.
It had no effect on the wattmeter jumping figures.
Perhaps a snap on ferrite choke on your chargers DC output can help determine whether charger is an RFI/EMI emitting noise making device that is confusing your BMS.
Some older USB cables or power supplies/chargers have removable snap on ferrite chokes on dc outputs which can be cannabialized.
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