Nano-Techs unbalanced

[Wingnutz]

Several Nano Tech batteries purchased last season will not balance or stay balanced. I'm a relative newcomer to RC so I'd be the first one to suspect owner mismanagement as the culprit.
1. I balance charge at 1C every charge.
2. I generally run the batteries down to 3.7-3.8V/cell.
3. I use two different chargers, one is an HK multi charger with a separate AC power source or an automotive battery, and one is a single battery charger which can connect directly to AC or DC.
4. Because of a number of health things going on at the end of 2012 flying season, most of theses batteries were left fully charged until early this spring when I got around to "winterizing" them.

When these batteries are put on balance charge, the charger doesn't shut off and indicate FULL as it used to.
Rhino and. Turnigy batteries I have are fine.

Anybody else having Nano-Tech woes? Anybody have an answer or remedy to my unbalanced Nano-Techs?

How much of a discrepancy in cell voltages is healthy?

[bfeist]

I've heard about nano-tech batteries disliking being left fully charged. I suggest "storage charging" them (puts the packs down to 60%) and balancing them from there. I believe over time they will balance better and better. After each day at the field, put your packs back to storage charge and balance them there, then charge just before you go to the field or before your flight. I may have just gotten lucky, but I have nano-tech batteries that are 3 seasons old and still going strong.

[Skyking]

Hi Bill,

I have always left my nano-techs fully charged and have never had a problem but storage charging is reccommneded.
Is it possible that you are a little bit unbalenced ?

Your friend

Ken

[Wingnutz]

Hi Bill,

I have always left my nano-techs fully charged and have never had a problem but storage charging is reccommneded.
Is it possible that you are a little bit unbalenced ?

Your friend

Ken

Possible? Possible? CERTAIN!

[MarcV]

I suggest "storage charging" them (puts the packs down to 60%)

"Storage charging" usually charges a battery to 50%.  If the battery is charged above 50% then you might need to discharge the battery either by running it in your plane or using a charger with discharge ability.  If you left the battery fully charged for a few weeks then it's internal resistance will go up, I don't know why it would cause a balance problem unless the increase in resistance is substantial, in that case the battery should not be used in an aircraft.

After charging the battery, measure each cell's voltage.  If they're all within 0.05V of 4.2V then the battery is fully charged and somewhat balance.

Marc