Lipo wont stop charging

[RedOctobyr]

You don't necessarily need a properly-balanced pack (done on a different, known-good charger) to check whether your charger is calibrated. I'd argue all you need is a multi-meter (calibrated would be nice, but most of us don't have that).

Check the voltage across adjacent pins of the LiPo's balance lead. Compare the multimeter readings to what the charger reports. If the high cell is confirmed as being high (eg- 4.20V vs 4.16V for the others), then your charger is reading correctly.

I'd be more concerned about the *difference* in reading between the different cells, beyond just the readings themselves.

If your multimeter reads the same each time on the same cell, and reads a difference of, say, 0.04V for a certain cell, vs the rest, then it's probably fair to say that this cell really is 0.04V high. Whether your meter reads it as 4.20V, 4.18V, 4.22V, is likely more related to calibration. But if the meter reads the same cell consistently as the same voltage, then you can likely trust relative readings, at least.

Also, suspecting charger calibration (in a case where the charger can't bring a cell into balance) seems a bit questionable to me. The charger merely wants to make them all *read* 4.20V. If that means they're really at 4.15V, or 4.25V, doesn't really concern the charger (it can't know that anyhow). It will just keep working on a given cell until it reads that cell as 4.20V, regardless of whether another device would confirm it's actually at 4.20V.

Admitedly, poor charger calibration could make it take longer to get the LiPo balanced the first time, as it would be trying to fix a significant "imbalance" that doesn't actually exist. .

[Michaelinpr]

Originally Posted by Mr.Andersen

I assume users speaking of calibrating their chargers have calibrated equipment to messure the actual voltage.
I would not thrust a cheap instrument for that, only industrial grade instruments.
Imagin now you calibrate your charger to charge above 4,2V, like 4,3-4,4V.

I usually double check my Multi meter and the two voltage checkers I have against a known voltage. I totally agree with you though. People need to check there testing equipment. There are a bunch of the same cell checkers at the field and they are all over the place.

[Gregor99]

Originally Posted by RedOctobyr

Also, suspecting charger calibration (in a case where the charger can't bring a cell into balance) seems a bit questionable to me.

Calibration (initial and drift) on the inexpensive 4-button charges is notoriously questionable. Its not as big of an issue on some of the better brands.

In the OP's case, its not likely due to calibration. But wouldn't it be a horrible thing if he later found out the "low cell" was actually being overcharged once it was balanced (according to the charger). Again, not as likely as the new pack syndrome, but still worth checking off the list.

On the DVM, I used to not include "calibrated" when I recommended that. But there were there some that did not like that and would ding me for it. The truth is that the cell checkers and chargers use a multichannel checking method which can be easily faulted due to difference in resistance between the balance connections (wires and connector). Using any DVM (calibrated or not) one cell at a time is not impacted in the same way and will give far more accurate results. As you point out, you may not end with 100% voltage readings relative to an external reference. But you will end up with readings which are 100% relative to each other, that's really what is important.

[Diggiz]

Ok, So after 2 more cycles and charging the lipo at 1c It finally bought all the cells to 4.20.
I did take 75mins though, But at least they are the same, so I will do one more charge at 1c and then 3c with the others after that. And hopefully the time it takes to charge will reduce now as the cells are even now.
Thanks Guys
Will let you all know what happens after that.