that all depends on the bms theres isnt an universal answer you can give about this topic you need to know the exact bms model
some balance all the time some not, some only when charging etc
This part bugs me. lithium ion doesn’t like being left at full state. 4.25v is slight overcharge. Days. It feels like trading convenience for pack life. Sigh.
Wouldn’t it be nice if there was a balancing device that worked by charging the low groups instead of discharging the high groups? It’d be hella slow but surely faster than the typical 50-100ma bleed current too.
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It’d be hella nice. It’d also be more complex with more parts to fail. 
There’s always a tradeoff.
Most of the time I only charge to 4.15V / cell and every 5 charges or so to the full 4.20V / cell
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I use a usb powered 1p charger to bring low groups in line - loads quicker than waiting for BMS to do it I would imagine?
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There was a balancing collapse of 0.4V at the maximum between P. I used this to make the cell balun uniform. But it was not good. It was balanced to a certain extent. Even if I connected the 42V charger afterwards it was not fully charged. Is it possible to balance by keeping the charger connected for a few days?
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agreed. i actually asked bestech if we can modify the module so the float charge occurs at a lower voltage - answer was no.
definitely! if i was better with an arduino, i think it’d be relatively simple to put together a prototype that charges each P group until it comes up to a specific voltage (ie 4.1v). essentially a bottom-up charge scheme as opposed to top-bottom charging.
i think an opportunity was missed here when this bms was put together. it’s just like a fancy bms with a bunch of features i don’t really care about.
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The problem I think is, for each charge circuit, the ground needs to be floating. Perhaps if the charger charged a single p group at a time… Like, bulk charge until 1 group hits the defined max, then charge individual groups one at a time. It would take FOREVER with the CV stage, but might still be preferable to the way it’s done now.
DieBieMS uses an off-the-rack battery management chip. So it would be a nontrivial change.
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yup, this is what i had in mind.
shoulda gone into electrical engineering instead of software…
The difference between the two is narrowing…
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Wow, i literally remember buying this bc its adjustable lol. Just bought my parts so long ago, i finally have a board lol. I see the adjustment “screw” just plugged it in and its charging at 49.4v and rising. Thx man…sorry not selling nowXD but what is the other adjustment screw for??
max current (“I” is the symbol for current)
Okay, i thought so. Just making sureXD… so for everyone else who gave me input too… should i get it to 50.4 and hold it there and bring it down to the 1.2 amp charge and like let it “drip” charge(sorta) the whole pack to balance it out, bc lower amps is healthier for the battery so to speak…correct?.. i also ordered a 4.2 v charger for that P group if the issue continues.
Made another thread here https://www.electric-skateboard.builders/t/12s8p-30q-cells-experiencing-voltage-sag-solved-fake-cells/76843 Title is the reason, and we determined they were fake cells. So yeah… i have however determine a 2 P groups 1 higher and 1 lower than the rests v. I will try mixing the 2 P groups cells to reach the mean i guess.
But how than all the one way cells work?
They sit for years on 4.2v till they sold and used.
Not saying that it’s no like that, just wondering.
Is there a study to it? I mean I read here everywhere that it’s not good to let LiIon and lipos left at full charge, but I couldn’t find any evidence to it yet.
If somebody has something about it I would be happy to read through it.
Especially with lipos it would be interesting for me.
At the moment lipos are my main power source and i can’t just charge them an hour before I go for a ride. So if I think I will go the next day I charge them up. If I can’t ride the next day I already have a bad feeling that it’s not good for the packs. But is it really like this? I also couldn’t find any recommendation how long I could let the lipo packs with a full charge. Just: not longer than needed…
Actually, i know part of the problem was fake cells… but tbh, that 1P charger is getting every P group pretty lined up. I think ill be with .003 V soon. Partial solution cedit should go here too, thx
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nope, they sit at around 3.5v for long term storage.
lithium batteries build dendrites as their cycled and the higher voltage accelerates this buildup.
look up “lithium ion dendrites”
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Just to reiterate, the seller of the fake, fraudulent 30Q cells was
bought from dhgate website
So anyone who finds this, never buy cells or anything else from there
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glad to help
and if you accidentally over charge I used something like this, did the jobs pretty well without too much heat
https://www.amazon.co.uk/Witmoving-Headlamps-Flashlight-Headlight-Camping/dp/B074VVP4QT/
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I never bought one way cells which where charged only to 70%
lipo or liion?
samsung liion cells come out of the factor at 3.5v.
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