lipo voltage diff between cell

I,ve a FlightPower 3s pack that cell number 2 is lower than the other, but this is arrive just this week. I have charge my pack monday, all the cells was equal. Tuesday i,ve play with my truck and dump the pack thru the LVC set at 9.6 volts. Reinstall the pack on the charger and .......the cell number two have a 0.075 volts of difference with cell number one and cell number 3.

What can cause this and is the difference is too much???

What can i do to resolve this??

Thank you

[phatmonk]

Good question? I recently bought a 4s 5000 MA battery and it has been charged only 3 times and I balance charged it. And it allways has 3 cell lights on and hasnt balanced out when all the lights shut down even at full charge.

OK my pack is on the Hyperion now since about 30 minutes, on the balancer mode only.
Now the cell number 1 is 3.630
2 is 3.619
3 is 3.640

The gap voltage is now at 0.020.

So the cells is to be balance, but when i reput it on the charge, the cell number 2 always retake his 0.07 volt gap

[MetalMan]

The balance of the cells in a pack isn't really important when the pack is discharged. The closer the cells are at the end of a discharge just tells you how well the cells are matched to each other.

Well, this is the problem.....i've always have same voltage on each cells on this pack at the end of the charge, but for any reasons, when i've charge it tuesday after a 30 minutes of bashing, the cell number two was 0.06 volt lower than others.

[BrianG]

Probably a slightly weaker cell. 0.06v is not much different TBH, but would still be nice to get perfect. May check the balance connection you are measuring from. If dirty, it could account for a slight dip...

OK Brian, but i don't think that's dirt in the connection, because when the pack is connect to the charger by the balancer harness or if i take a multimeter to check it, i obtain the same reading. No matter if i pt the multimeter lead IN the balancer connector or on the tab on the connector

Anyways, i've balance the pack this morning, and now, i'll put it back on the charger and see how it'll be at the end of the charge.

Is the fact to run with an unbalance cell in a pack could cause it to puff????

I've got this exact same thing happening to a 3s truerc pack i got last week.. cell 1 is always lower than 2 and 3.. I balance before charging, and when I take it of the charger cell 1 is low by ~.05v.. I can't balance while charging because I'm using astroflight's. when I first got the pack, cell 1 was chillin at 2.5v.. the others were around 3.5v.. I just slowly charged at 1/2 - 1C until the pack was 1/2 charged, took it off and balanced, then continued charging at 2C. so far the pack's been running great, I dunno how long it'll last though w/ that one cell.. I'm not sure how many amps i'm pulling, but the pack's only rated to 80amps =\.

ok just charge the pack, during charging, it,s the cell 2 (the one who,s lower normally) that was the higher during charge but not too much, about 0.017 v of gap.

I,am thinking that this cell have a lower internal resistance and discharge and charge faster than two others one.

[suicideneil]

Something like that I imagine, but that really is such a small difference I wouldnt worry about it myself. I always seem to have nearly 0.1-0.2v of difference between some cells when discharged, but they all finish up equal when fully charged so its no problem.

When my pack have finish to charge, all was OK, all the cell was at 4.2V.
I'll run the pack like i did before..........

[MetalMan]

Originally Posted by A4DTM

I've got this exact same thing happening to a 3s truerc pack i got last week.. cell 1 is always lower than 2 and 3.. I balance before charging, and when I take it of the charger cell 1 is low by ~.05v.. I can't balance while charging because I'm using astroflight's. when I first got the pack, cell 1 was chillin at 2.5v.. the others were around 3.5v.. I just slowly charged at 1/2 - 1C until the pack was 1/2 charged, took it off and balanced, then continued charging at 2C. so far the pack's been running great, I dunno how long it'll last though w/ that one cell.. I'm not sure how many amps i'm pulling, but the pack's only rated to 80amps =\.

Balancing before charging isn't going to help an end-of-the-charge imbalance, it will only make it worse. That is, unless your pack is made up of cells perfectly matched for capacity .

Wait, why can't you balance while charging?