Huh, will update if I remember where I got that or find anything useful in the morning then but this sound right
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Would be interesting if you swapped BMS and it fixed it, but if cells are self discharging idk.
are there any like cell health testing machines?
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I’ve been wanting something like this for years. just something that can tell me the pgroup’s actual capacity.
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huh wait you mean like built into the regular BMS so it can perform a check on each pgroup overnight?
what you said sounds just like cap testing a pgroup through the balance leads.
I was thinking some kind of specialized machine that carefully measures the cell compared to a baseline measurement idk. Some magic is what I want.
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Yes, there are but “health” can be measured in different ways and usually involves multiple tests. These devices are frightfully expensive.
Basic capacity and DC internal resistance checking can be a good overall indicator of health though. Tracking their changes over time can indicate when a pack (or a p-group) is reaching the end of its life. But loss of range is a good indicator too and needs no equipment. 
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All of the LiPo hobby chargers can measure capacity pretty accurately.
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god dammit what we want is a magic computer that measures them all in a second and says exactly when it will start drifting so we can adjust our warranties.
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Wide open throttle WOT
After top balancing yesterday I rode today and the divergence narrowed down to 0.015-0.020 even during slight acceleration and not as bad during WOT maybe 0.04 max
Seems like it’s just normal cell wear and p4 is leading the pack?
Atleast it didn’t get worse. Maybe after some cycles it should normalize more and more
It was just surprising that after 2 or 3 weeks of no use when it was at 0.01 even during WOT before and after this happens randomly without use
I thought even maybe the BMS draws its current from p4 over 2 weeks draining it. But does it even use power while not in use?
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The bt module is always switched on as long as the balance wires are connected to the bms.
So yes there will be always a small current draw from the bms.
Do you know which P group it draws from?
Most (all?) BMS circuits have their negative attached the bsytety negative to use as a reference for obvious reasons, and then tap their power off the battery positive. Drawing/isolating power from one P group would be quite tricky because it’s hard to intentionally get current to flow through just one part of a series-connected circuit. It just takes from the whole battery.
Umm….but…that is exactly how a balancing circuit works.
It’s not any harder to pull from any part of a series-connected string of cells.
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Yeah sorry I meant take current from between two nodes at say 12V and 8V relative to battert negative and use that current in a circuit that’s already also referenced to battery negative. It’s easy to take an isolated resistor that’s not referenced to “ground” and dissipate a current as heat to balance out a P group, but not to use that current for logic referenced to ground unless you want to make an isolated converter.
That’s what I meant, but I’m now less certain that it’s right
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If I understand you correctly, you’re definitely right.
Using the 12V/8V taps you mentioned for a circuit it would be a very bad thing to connect that negative (which is at 8V) to another circuit’s negative that was at zero volts.
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Yeah so what I was trying to say was you can’t take power for the IC/BT/whatever just from the 12v/8v source which would be group P3, because OP was worried about power being drawn solely from one P group and causing the imbalance. You can take power to balance them, but it’s not realistic to take power to run another circuit with a common negative
Right I asked a dumb question. I see that now
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Not dumb at all. None of us knew any of this until we learned it. 
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I just wanted to chime in and say…
… Relax.
You are only worrying about this as you can see it on an app, this is one of the worst things about having a smart BMS - it can make you paranoid. Want to know how often I check mine? Almost never, I’ve probably checked it 3 or 4 times in 12 months.
The BMS is set (as default) to balance to a precision of 30mV - so all that time when your pack was under that threshold it never balanced the pack, consequently it will drift apart slowly and this is what you have seen now its at 40mV delta. A 40mV variation across 12 groups is almost nothing! It’s incredibly in balance. The BMS is doing its thing and the batteries are doing their things. It’s almost Impossible for 12 groups of cells to be exactly the same, even the manufactures give cell variances of +/-10%.
So keep an eye on it but don’t worry about it!
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sweet deal my friend, thanks for the reassurance. I am subbed to your Youtube channel btw. Still waiting on that 16s 4wd? or 2wd you promised long ago lol XD
My packs calm down to 0.015 and 0.02 or so resting, so not getting progressively worse at least. Will stop checking the smart BMS app, it’s so addictive…
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Ah man, the 16S board is basically done, but I just have no motivation to ride it at the moment.
I’m working on some other stuff which I think is much cooler. Next video will be on the TTL system
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