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Batteries & Chargers Discuss Li-P, Li-Ion, NiMh, Nicad battery technology and the chargers that juice 'em up!

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Old 02-16-2014, 09:59 PM   #1
Henry111
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Unhappy What does "20C" on battery stand for?

There is a Dymond Modelsport battery on which the label reads:
Receiver battery LIFE
2S1P
6.6V/2100aAh
20C
What does that "20C" mean?
Also: What does the word "LIFE" stand for?

Henry Holcomb
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www.ElectricFlyerMagazine.com
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Old 02-16-2014, 11:18 PM   #2
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Old 02-16-2014, 11:34 PM   #3
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Old 02-17-2014, 12:10 AM   #4
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Originally Posted by Henry111 View Post
What does that "20C" mean?
20C is an indicator of the maximum recommended discharge rate. C=Capacity. So 20C is rated at 20*capacity discharge.

So if your battery is a 1000 mAh pack you can discharge that at 20 amps safely.

Take them with a grain of salt - many times it is pure marketing.

Originally Posted by Henry111 View Post
Also: What does the word "LIFE" stand for?
LiFe stands for Lithium Iron Phosphate or LiFePo4

http://en.wikipedia.org/wiki/Lithium_iron_phosphate

These are normally used for receiver packs - not for power systems (in 2s at least).

In larger voltages they can be used for flight packs however. They come in two types - flat packs, similar to LiPoly packs and "round" cells. The round cells are in fact used in many hybrid cars. They are very capable, offer 1000 charge, discharge cycles and can be charged at very quickly.

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Old 02-17-2014, 01:27 AM   #5
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Originally Posted by Henry111 View Post
There is a Dymond Modelsport battery on which the label reads:
Receiver battery LIFE
2S1P
6.6V/2100aAh
20C
What does that "20C" mean?
Also: What does the word "LIFE" stand for?

And, some more info on that confounded "C" terminology.

"C" and what it is
http://www.wattflyer.com/forums/showthread.php?t=65869

Problem with some of those batteries rated at "60C" or higher, if you actually fly a full flight while running your battery at 60C, you've got one minute of flight time before your battery is completely discharged. And, how knows, how hot it got.

IMHO, 20C for a LiFe battery is a bit optimistic. More reasonable to run at a maximum of 10C or 20 Amps for your 2000 Mah battery. That is plenty enough current capability to run even a giant scale model. But, giant scale models require much larger capacity cells, along with dual batteries for reliability.

That said, for me anyhow, LiFe receivers work very well as receiver power. Their voltage discharge curve is virtually identical to a quality 5 cell Nickel Hydride battery pack. When you get to giant scale models where the peak servo currents can hit over 10 Amps, LiFe batteries far outperform a five cell "AA" type Nih battery pack. I've got two cell 2300 Mah A123 battery packs in my two giant scale models for receiver backup power.

LiFe's don't work well as electric motor power though. They simply can't handle the higher currents. For electric power, go to the similar chemistry A123 cells, or LiPos.

DennyV
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