Is my lipo dead?

[Mathew]

Hi newbe here. I discharged a lightmax 2650 20c 22.2v (zippy) battery today, when it had nealy finished noticed that 1 cell has more volts than the others. Didnt thing much about it till i went to charge it and the charger only found 5 cells? Help!

[tourerjim]

Its not good to discharge lipo's, balance charge then see what each cell is.

[coolice]

Hey.

It could be you've over discharged the pack and its got out of balance, or that cell is not so good as the others. The problem comes now if your charger needs to see the pack as a 6s to charge properly.
A trick to bring over discharged packs up to voltage is to gently charge the LiPo as a NiCad pack, however its risky and so only attempt it outside or somewhere safe if needed.

If you can though just let the charger keep charging and balancing until done.
.

[Wayne's World]

Hi Mathew,

You have slightly over-discharged the pack, so the charger is seeing the low voltage and thinking its a 5 cell pack. The pack should still be okay, but you need to raise the pack voltage. The easiest way to do this is to start charging the pack with the charger set to Nicad/Niamh, say about half C (half the pack amp/hour rating). You MUST stay and observe this and stop the charging once the output charge voltage passes 23v. You should be then able the charge the pack as per normal.

Wayne.

[cjcj1949]

That's unusual. One cell is .3V above the others. Usually one cell is low. You should be able to do a normal lipo charge (no balancing) (0.5C).Use LiOn or Life for extra safety then it won't charge so high. Do check the temp of the pack all the time. Once you get a few hundred milliamp hours in you'll find that the volts difference is much less. Then you should be able to get the charger to see six cells and do a balance charge. You may have another fault though. I can't explain one cell high otherwise.

Chris

[coolice]

Hey.

Looking at your pictures again there is no reason why the charger should not see the pack as a 6s, reason being all cells are above 3 volts each which is the lowest voltage a LiPo cell can be discharged to.

The difference in cell voltages I think is down to the differing resistance within the individual cells which make up the pack, a lower resistance gives its power away easier than one with a higher value and so discharges quicker.
I think I see this with the 2x 6s packs I use in my 700E.
.