I have had since spring a set of 7, TP 5 cell 2600 batteries.  I didn't  flyi for a bit and came back and found that I now have 4, 5 cell batteries and 3 that have switched gender to 4 cell  Each of these batteries had a cell die.  What did I do wrong.?  Is is typical for one cell out of a pack to go bad?  If I leave a battery that is completed charging, inadvertently left to idle on the charger too long, will it drain back through the output of the charger?

Also, since the battery thinks its 4 cell, can I use it as a 4 cell?

I have had since spring a set of 7, TP 5 cell 2600 batteries.  I didn't  flyi for a bit and came back and found that I now have 4, 5 cell batteries and 3 that have switched gender to 4 cell  Each of these batteries had a cell die.  What did I do wrong.?  Is is typical for one cell out of a pack to go bad?  If I leave a battery that is completed charging, inadvertently left to idle on the charger too long, will it drain back through the output of the charger?

Also, since the battery thinks its 4 cell, can I use it as a 4 cell?

Frank:
I had a TP 5s 2800 register as a 4 cell on my charger and refuse to charge.  On the battery checker it showed 5 cells, 4 at around 3.5v and one at 1.2v.  It would not charge, balance charge, discharge, or storage charge but it would "balance".  I left it on balance till the good cells approached 3.0 and it came up to 2.4, just under the li-ion threshold.  I tried a balance charge as a li-ion and it worked.  I let that run till I was over 3.2 on all 5 cells then shut it off and balance charged as a Lipo.  It is back at the tail end of the rotation, but I suspect it will die of old age sooner than the rest.

Ken

Thanks Guys for your inputs

The batteries are more than 6 mos old,,, so no warranty

Hi.

Before condemning the battery, make sure the sum of the cells is the same as the battery voltage.

Then, with the aid of a multimeter, measure the voltage of each cell directly on the balancing connector.

This happened to me last week A new battery was left with a cell at 1.25v. It was an issue with an extender cable that I use for charging. I was puzzled why the charger showed the cell at 1.25v and not Ov. But there must be an explanation for this.

DouglasB