Questions

[Adam Glatt]

Jeff Hughes wrote:

> OK, I keep getting the urge to build an electric 2M. But the price of 
> LiPoly's are still out of reach ((not even bringing up the care and 
> feeding dangers of them). Has anybody figured out what the weight/cost 
> penalty is between the lipoly's and Nimh? I don't need 30 minutes of 
> flying time, only 12-15 (I fly advanced). Most of the glow planes I've 
> built lately have come in around 9.5lbs, so I've got a lot of room to 
> work with (weightwise). How much do you give up with Nicads? I'm 
> really not into this, but it seems that you could outfit a 2M with 
> Nimh or nicads for around 30 or 40 bucks. Am I missing something here?


lipo 10s3p  - 33volts, 5ahr = 165Whr
Nimh gp3300 - 1.15volts/cell, 3.3ahr = 3.8Whr/cell works out to 43cells 
to store the same energy.
^All rough average quick numbers, of course.

Thunder Power lipo costs $680 and weighs 1.1kg.
Epic GP3300 costs - around $220 and weighs 2.7kg.
That is a weight difference of about 3.5lbs.

And that is ignoring the problem of parralleling NiMH batteries (as I 
understand it, this isn't supposed to be done), and how much extra 
energy would be required to carry those 3.5lbs, and the decreased 
voltage caused by cold GP3300s.  I think the GP2200's have a higher 
energy density, so they might make the numbers a little better, but the 
point remains.
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