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Jul 04, 2016, 03:53 PM
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DonA's Avatar
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One dead cell in lipo pack?


Here's a question for the group. A friend has 2 6S 8000mah packs that have both dropped cell #1 in each pack. Both exhibit the same characteristics. A few flights running the 6S packs in series (with other packs, not together) and cell #1 in each has dropped to zero voltage. The other cells in the faulty packs are fine. I have never had this happen, how can a cell go to zero voltage? Basically it acts like it is shorted. The total pack voltage matches the total of the other 5 cells and they check fine.

Don
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Jul 04, 2016, 03:58 PM
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Yes, it's possible and I've seen this before. In the occurrence that I witnessed, the charger that was used was well out of calibration and the cell that went bad was being undercharged by a good amount, despite the charger displaying all cells at full charge voltage. The subsequent discharge resulted in overdischarge and damage to the pack.

Other possible causes are defective pack or pack damaged due to handling, installed condition, etc.
Jul 04, 2016, 04:28 PM
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Yeah, this is weird. Charger works successfully with other 6S packs, many charges. The really weird thing is it is the same cell in both packs. Oh well, chalk this one up to just plain weird..... ;-)

Don
Jul 04, 2016, 04:49 PM
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ok chargeing and discjarging are two different things.. op did not discharge thru charger... i have has last cell in pack go bad b4 not 1st defective battery is my guess...mrsforth says charge was over v in 1st cell then says discharge function did it so what is it? id say again bad battery also replace charger if possible!
Jul 04, 2016, 07:12 PM
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We decided to chock it up to coincidence (#1 cell in both packs). Charger was used for 6 months before this incident and many times since without issue. Charging rate never goes over 1.5C and discharges never went below 3.7V. No cells puffed, even the 0 V ones. All other cells are 'normal' in both packs. Charger is iCharger 4010 Duo

Thanks for the suggestions

Don
Jul 06, 2016, 05:59 PM
jofro
It happened to me so many times over the years that I take it now as a normal thing with lipo packs. Easy fix, just remove the bad cell and use it as 5S pack in different set up. You know the old saying, you always find bad egg in the basket. In my case it was just about always the cell on the negative side.


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