Something is wrong with your charger. What charger did you borrow?
Measure a brand new Alkaline AA cell. What voltage do you get? Is your measuring device the thing that’s not right?
1 Like
That’s the issue, you can’t easily tell if it’s working or not. At minimum it needs a fault indicator, loud beeping or blinky lights…
And bypassing BMS for discharge gets rid of 50% of the safety factors.
I’ve been thinking about this for a long time and trying to convince myself, but I’m still not convinced. 
I’m going to wet my toes with one of those bluetooth Smart BMS, just to monitor voltages. Then add it to the charge circuit. Then maaaybe add it to the discharge.
This is like the “I used to know what time it was until I got a second clock”. I ended up buying a voltage reference…
1 Like
li ion cells are safe from blowing up all up to i think 5.x volts (i read this on some paper can not find it now) higher than 4.2 is just slowly ruining them
Didn’t have a brand new AA, but I measured a brand new 9V and got 10.33V… I then switched out the battery in my multimeter and read a 9V as 9.58V which from what I read is ok. I measured my charger again and it’s 42.1V.
SO the multimeter was reading incorrectly. Here are the new readings from my 10s pack.
3.8 3.8 3.9 3.8 4.2 4.2 4.2 4.2 4.2 4.1
Much better, but why would some of those be lower?
Anyway, here are some pictures of the wiring, like @Eboosted wanted to take a look at.
2 Likes
This is great news. 
So your charger and BMS may be working correctly after all – but not your multimeter 
So I would let it sit on green for 10 more hours and see if any of the low cells go up, or if they don’t. That would determine the next steps
Maybe check after 15 minutes, 1 hour, and 4 hours
To be clear, you’re looking for a 0.2V jump because 0.1V is the resolution limit and could just be rounding errors.
1 Like
The difference is so big a bms won’t be able to balance them back. I would manually discharge the higher ones to get them close to 3.8v (use a light bulb connected to the individual groups that are high in voltage).
Once you manually balance them, if the bms works it should keep them in sync.
1 Like
IMO not slowly at all at 4.5v. But whew!
Still begs the question of why they went so far out of balance.
The balancers on BMS, once they trigger, do they run until all cells are in balance no matter how long it takes? Or only if charger is still supplying power?
Where I’m at right now in my understanding is, the charger has to deliver full pack voltage, but not enough to trigger pack over-voltage-protection. The balancing will be triggered when one of the cells reaches the balance-start voltage (probably 4.25v on this bms?). As long as charger is still supplying power, the BMS will attempt to drain all cells down to the voltage of the lowest cell.
The charger will continue to supply power until the entire pack’s voltage hits its setpoint. This should not occur until all cells are balanced and full.
If something goes wrong, the BMS will open the charger circuit, cutting off power, and the pack will not be balanced or fully charged. One of the possibilities here is the charger is supplying power faster than the BMS can drain the high cells down. This should not happen if cells are close in voltage, as the charger will not provide a lot of watts to the pack when the pack is near full.
Someone correct me if I’m wrong.
1 Like
this depends on the bms some bmss balance all the cells to be at the same voltage every time like on 4.2, 2.8 or 3.2v and some only on full charge as i know
1 Like
Either way, I’m thinking if you use a CC/CV power supply instead of a lithium ion charger, once the pack is full you’ll be constantly running the balancer until you pull the plug? More BMS caused premature wear, if you don’t have full understanding of your BMS behavior?
Let’s wait until all the facts are in before we rush to judgement
We still need experimental results else this could be speculation
theres a whole discussion about this on here
2 Likes
Ok I let it sit with the charger on green for about 16 hours. Not much changed.
3.8 3.8 3.9 3.8 4.2 4.2 4.2 4.2 4.1(decreased .1) 4.2(increased .1)
Instead of hooking up a light bulb to the higher voltage packs, could I use my Imax B6 charger and charge them all individually to balance?
1 Like
You could use the B6 on each P-pack yeah
Somehow your setup is not balancing your cells. It’s like the charger is not doing the CV part of the CC/CV cycle.
Those two changes could be rounding errors. If the minimum granularity of your measuring device is 0.1V then you need to see a 0.2V jump to be certain it has actually changed.
I would borrow a charger and try the same experiment again. If you get the same result then I would change the BMS.
The balance charging part of the cycle is not happening
1 Like
Honestly I WOULD NOT use the B6 to manually balance the cells. The reason being is because that will work once, but you want to fix the problem, not kick the can down the road. If they are all perfectly balanced you won’t be able to test the balance charging…
1 Like
I’ll hook up another charger for a while. I just sent an email to Lilian at battery supports to see what she thinks.
1 Like
Would have discharging through the BMS helped keep the P-packs more balanced?
Probably not, I used that exact same BMS once and after around 2 months of running it without being bypassed the thing blew up on me.
2 Likes
so what i seeing, the bms stop charging after just 1 cell is reached 4,2 V and the others lower than 4,2 stop charging… this is a shit. maybe the discharge is the same, when a cell is 3V, the discharge close, and you can’t ride anymore if the others 9 cells is 4V…
1 Like
Achivement!! Welcome This badge is granted when you receive your first like on a post. Congratulations, you’ve posted something that your fellow community members found interesting, cool, or useful!
I want to say thanks to my mom, dad, and all my friends who stay with me in my bad and good momens, and a big thanks to my follwers. I love you <3
1 Like