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Old Apr 02, 2013, 05:50 AM
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Little Black Duck's Avatar
Thornleigh - 20k N of Sydney,N.S.W.,AUSTRALIA
Joined Aug 2001
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Help!
Possible dumb enquiry

G'day all ...
Some advice please. This may have been asked before ... If so I apologise.
Aircraft - 2m ARF e-Sailplane, TOW around 1.2kg depending on LiPo used.
Advice - At present I'm using a 3S 1800mAh Nano-Techs.
I've been advised on one hand to use larger 3S 2200 or even 2650 size LiPos, which with careful positioning still fall within the CofG range when fitted despite their extra weight, which would give additional flight time, and possibly better penetration.
On the other hand I have been told that even the 1800s are a little on the large size, and I should actually use a Smaller 3S LiPo of around 1500mAh or even go as small as 1200 which would supposedly improve performance, as well as lightness.
Appreciate any opinions please ...
Daffy.
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Old Apr 02, 2013, 06:52 AM
Space Coast USA
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Space Coast
Joined Oct 2000
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Larger batteries = longer flight times (under power), better wind penetration, higher wing loading.
Smaller batteries = less flying time*(under power), better thermaling capability, lower wing loading, better floater.

* you actually might get much longer flight times if any thermals are present as the lighter glider with the lower wing loading will thermal and float better not needing any power.

Get one of each, the 2200-2600 for windy days and a 1200-1500mah for calm days.
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Old Apr 02, 2013, 09:58 AM
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United States, VA, Purcellville
Joined Nov 2011
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Hoppy's advice was spot on. Keep in mind what you're really gaining with the higher mAh. Below is a technical summation of the differences;

Nano Tech : 1800 weight approx 161g and calculated WOT flight time is 4.90 min

Nano Tech: 2200 weight approx 187g and calculated WOT flight time is 6.00 min

all things being equal (wind, drag, speed, operation etc.) the delta of 26g which is just under one ounce heavier will yield longer performance but not necessarily greater performance.

Something to think about is the new G3 series from Hyperion. These are getting great reviews and offer substantial mAh with low weight and size. Moreover, these batteries can be charged at a rate of 5 (recommended) or 6 (suggested) C!
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Old Apr 02, 2013, 07:01 PM
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Thornleigh - 20k N of Sydney,N.S.W.,AUSTRALIA
Joined Aug 2001
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Thanks to both Hoppy and Tank,
I tend to think that the relatively small difference in weight would not make any real difference to overall performance in a 2m e-sailplane which has a relatively large wing area.
However it would increase flight time substantially as, obviously with a sailplane, during most of the flight, throttle would either not be used, or only with sufficient throttle to climb out of sink, or for initial launch, where the additional capacity could be used for more power (current draw) if required, although even then I've seen that WOT is rarely be used.
Have I got that right?
Daffy.
P.S. I like Hyperion LiPos too, but they're too expensive here in Oz in comparison to either Nano-techs or Rhinos. Limited funds y'know!
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Old Apr 02, 2013, 10:29 PM
Space Coast USA
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Space Coast
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Quote:
I tend to think that the relatively small difference in weight would not make any real difference to overall performance in a 2m e-sailplane which has a relatively large wing area.

A 3s2200mah Nanotech weighs 201g where as a 3s1500mah Zippy Compact weighs 113g
3 oz difference.

That is probably 10% of the total weight or a 10% change in wingloading.

You might try the ZIPPY compact series. They are light weight, smaller than similar mah packs and have performed OK for me.
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