It’s dependent on BMS, but take a look at the spec sheet here
You’ll see that it has an over-charge protection which is accurate to +/- .05v. Some BMS’s might have a wider tolerance.
You can check the balance lead directly to see how much voltage it’s giving off. It will never up the voltage on your cell higher than that.
This video has a good explanation of how bms work.
So I left it charging for an hour. It didn’t charge anything anymore. So the cells are still unbalanced. According to that video (what I’ve read before), the bms sheds the voltage of the 4.2 cells so that they lose while the gain, neutralizing each other. But where does that discharge current go?
Have you checked all the balance leads to make sure they’re giving off 4.2v?
While it’s charging? I’ve checked them all one by one while not charging and the voltages I saw are what I posted last night.
I mean not for the cells, but from the BMS itself. Unplug the balance JST and probe each balance lead port to see check the voltage
yes, that’s what I have always done. That’s how I came up with the voltage of each cell.
Again I don’t mean checking the voltage of the cell, but the voltage on the BMS. If you’re saying your getting 3.9 on some of the BMS balance leads then it sounds like the BMS is malfunctioning.
I get nothing. It doesn’t show any voltage between pins of the balance port without being plugged in. And I don’t see why it would, there’s no positive connecting the battery to the bms. The balance leads are that positive. So why would I get any voltage like this?
unplug the JST and measure from the balance port
I get nothing…
is it plugged in?
With the JST unplugged, and the negative from thebattery plugged in, I get nothing, because the circut is incomplete. Theres no positive going into the bms. The only positive meant to go into this bms is balance wires. Which is why I’m confused as to how I would get any voltages without the balance plug plugged in.
you can measure it with a multimeter, probe the positive to balance lead and negative to B- on the BMS.
I did that, but I’m getting nothing.
Darn, thought that would work. Have you tried with your battery turned on? but balance leads not plugged in?
How can parallel cells not be balanced?
bad cell
10 chars
The battery is not plugged into anything, including a switch. Was using dyi’s switch, but it was broken. So right now, it’s not hooked up to anything. It’s essentially always on. Does it matter if I removed the switch on the bms? could hat affect anything? cause I never had to turn it on to charge. But could having remove it caused this?
i still don’t understand how parallel cells can not be balanced, even if they are bad