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Old Mar 09, 2006, 07:11 PM
usual old know-it-all
Blackpool,U.K.
Joined May 2005
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Another lipo storage death?

My brother bought a Flightpower Extreme 3S2P 5000 about 18 months ago.
Used it for no more than 30 cycles on an Eco 8 heli for hover practise only.
Bat.definately no more than 20 amp drains,he could only hover.
Stored it after last run last october,got it out last week,after a long layoff.
Took 3400mah,started hovering again,after about 1 min,power rapidly started to fade,it would hardly lift off.Charged again,didnt take long and the same happened,no power.
I give him my F.power balancer last year so he used that too.
He tried his nicds and all ok,so not the heli.
I,ve more experience with lipos and flew right through the winter here.I told him to get the lipo out every week and fly at least once with it.
Am i right in thinking using them more often will prolong cycle numbers,in other words has storage with no usage destroyed his battery?
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Old Mar 09, 2006, 07:20 PM
Southern Pride
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Haralson County GA. USA
Joined Oct 2004
34,812 Posts
Two somewhat suspicious number here 5000 mAh capacity and they took 3400 mAh to charge. That makes me wonder how low the cells voltages were.
Most recommended storage voltage is 3.7-3.85 per cell.

The statement that only drew 20A as he could only hover is somewhat questionable unless he was in fact getting over 12 minute flights(?). Back when I flew Helis it took more power to hover than to fly around in forward flight.


Charles
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Old Mar 09, 2006, 07:32 PM
usual old know-it-all
Blackpool,U.K.
Joined May 2005
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Yes Charles,12 min hovers easily obtainable with a 5000mah bat,then in good condition.The Eco can hover at 18 amps,set up right.
His bat was stored after his last 'hover' and never touched,no idea of the voltage, then.
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Old Mar 09, 2006, 08:31 PM
Southern Pride
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Haralson County GA. USA
Joined Oct 2004
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Well I have experienced problems with packs from storage. I feel that it is best to charge at 0.5C and discharge at less than 30% of max. Cont. rating for one or two cycles when placing back in service. I have no hard data to susport this theory but it was suggested by a major LiPoly importer. I had one pack removed from storage which I cycled twice and first CBA Discharge test was awful. I cycled it three more times and it got much better. LiPolys are indeed strange.

Charles
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Old Mar 09, 2006, 08:47 PM
GPT
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Sydney,Australia
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Charles ,I,m a little concerned regarding storage voltage.I have been storing mine full charge for 1 to 2 weeks.For example fly one week charge the next day and fly 1 week later.They have not been stored at full charge for longer than 3 weeks at a time.Is this practise ok for the short intervals between use?
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Old Mar 09, 2006, 09:07 PM
usual old know-it-all
Blackpool,U.K.
Joined May 2005
1,315 Posts
Quote:
Originally Posted by everydayflyer
Well I have experienced problems with packs from storage. I feel that i I cycled it three more times and it got much better. LiPolys are indeed strange.

Charles
They certainly are unpredictable.He also brought out a 600mah2S pack,left fully charged,after the first of 2 packs crashed his shockie,from last september.When put on his Robbe charger it was still fully charged only taking 6mah!
I told him to cycle his Flightpower a few times,but he's since disposed of it in a disheartened mood.
I couldnt explain either bats.......
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Old Mar 09, 2006, 09:07 PM
Southern Pride
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Haralson County GA. USA
Joined Oct 2004
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Quote:
Originally Posted by GPT
Charles ,I,m a little concerned regarding storage voltage.I have been storing mine full charge for 1 to 2 weeks.For example fly one week charge the next day and fly 1 week later.They have not been stored at full charge for longer than 3 weeks at a time.Is this practise ok for the short intervals between use?
Most say yes and a few say no. My experience is that as long as they are cycled (used) often they are OK stored charged but then I tend to wear them out from frequent usage.

Newer cells seem to take extended storage better than older cells regardless of storage voltage. That is no surprise. Worst case seems to be heavily used cells stored fully charged for any length of time.

There are a few that feel that cell IR increase anytime cells are fully charged. This is believed to have the same accumulative effect no matter if the cells are fully charged and stored for 6 months. Or fully charged and used (cycled)once a week for 6 months.

Problem with LiPolys is that they are changing quickly and cells from last year and this years cells are most often very different.


I have packs which have been kept fully charged for over a year that are still doing extremely well. Most of these are frequent flyers.
I have packs which are a year old that have been kept fully charged that have lost their ability to deliver decent power that have not been used nearly as much.

Sometimes I feel that LiPolys have to be females. The best description I am aware of of a woman is. that of being consistently inconstant.

Best advise, purchase only what you need and use them often.

Charles
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