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HelicopterOff Topics › Can U use old LiPo battery pack?
07-11-2017 04:50 AM  12 days agoPost 1
C-Jime

New Heliman

Dublin CA

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I ordered a Gens Ace 4s LiPo battery pack back in 2012 (5 y.o) and since then it’s been just sitting in my attic without any use. The voltage on each cell is ~3.75V (was around ~3.8V back in 2012) and battery surface doesn't have any “puffing”. It it still safe to use for quadcopter/RC car projects?

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07-11-2017 07:32 AM  12 days agoPost 2
spaceman spiff

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Tucson

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I just checked out a few well used LiPos last weekend that have been sitting for about that long. Similar voltages. The charger says they are fine and still delivering 90% ish of rated capacity. I plan on taking it very easy on them for the first flight and see how it goes just in case. Makes sense to try yours on the car first.

I also had a few old nicads sitting around . They did not do as well. I "rehabilitated" them a year ago by rapid cycling them a couple times, with some success. I flew them maybe a dozen times, but in just a few months of sitting again they went to near zero charge, and right to the recycle box this time. I won't try to rescue nicads again.

You can't teach a crab to walk straight.

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07-12-2017 06:16 PM  10 days agoPost 3
ticedoff8

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Morgan Hill, CA. USA

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The failure mode on old LiPos is typically higher internal resistance.

If you application does is not pulling high current spikes or you are not trying to charge them at 3C, they may be fine.

If you have a modern charger, it may be able to measure IR (Internal Resistance)

But, if you notice they are more then just "warm" after use, then they are getting towards their end of life.

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07-12-2017 06:44 PM  10 days agoPost 4
spaceman spiff

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Tucson

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Excellent. I googled some more info. Found an article on Lithium battery life and performance. It went a little over my head, but the highlights are:
During charge, lithium gravitates to the graphite anode (negative electrode) and the voltage potential changes. Removing the lithium again during discharge does not reset the battery fully. A film consisting of lithium atoms forms on the surface of the anode called solid electrolyte interface (SEI). Composed of lithium oxide and lithium carbonate, the SEI layer grows as the battery cycles. The film gets thicker and eventually forms a barrier that obstructs interaction with graphite.

The cathode (positive electrode) develops a similar restrictive layer known as electrolyte oxidation. Dr. Dahn stresses that a voltage above 4.10V/cell at high heat causes this, a demise that can be more harmful than cycling. The longer the battery stays in this condition, the worse the degradation gets. The build-up can result in a sudden capacity loss that is difficult to predict by cycling alone. This phenomenon had been known for some years but measuring the coulombic efficiency can verify these effects in a more scientific and systematic manner.
Not fully charged and kept it cool? It is probably still good.

You can't teach a crab to walk straight.

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07-12-2017 08:31 PM  10 days agoPost 5
ticedoff8

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Morgan Hill, CA. USA

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Yep.

FYI: Most charger have a "Storage Mode" that will charge to pack to around 60% of capacity.

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Fake News will be the downfall of our Republic!

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