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Old Dec 29, 2002, 06:59 PM
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rc-eflyer's Avatar
St. Louis, Missouri, United States
Joined May 2002
1,446 Posts
Kokam 3270s and Race 280s

I'm considering the possiblity of using a single
Kokam 3270 on a Swift Racer that uses two
6V Race 280 Graupners on 4:1 gear boxes
turning 3-blade 9X7 props. When I static
tested one it was pulling about 4A at 7V. So
using this as a start I'm figuring probably no
more than 8A for both while actually flying.
This should keep me safely under 3C so I won't
be abusing the Kokams . The suggested pack
is 8X720mah NimHs. This pack weighs 102 gms
while the Kokam weighs 64 gms. I realize the
Nimh pack would be a little more voltage on a
fresh charge but with the Kokams my duration
goes up4 timesand I lose about 1.4 oz. weight!

This almost seems too good to be true, so am I
missing something
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Old Dec 30, 2002, 12:20 AM
Registered User
Gaithersburg, MD, USA
Joined Jun 2000
1,070 Posts
You can checkit with LIPOCALC at www.fmadirect.com/Store/Kokam Batteries/LIPOCALC You will find your design to work fine.
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Old Dec 30, 2002, 10:03 AM
Straight up is all I ask
Fairfield Ct USA
Joined Apr 2002
2,323 Posts
RC Flyer

I am sure the voltage drop from those aaa will be below 7v at 8 amp anyway and on top of that the performance will degrade to 35- 45 watts The Kolkam maintained 7.2 volts at 11 amps on my gws p 51 static and that was after i left my pack on a speed control over night in the on position oops . any way the pack charged back up to 2700 mah . BTW where are you going to put those cells ? The fuse looks a little tight . Wings? James
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Old Dec 30, 2002, 11:41 AM
Official Old Git!
Hampshire, UK
Joined Sep 2000
1,422 Posts
rc-eflyer,

"I'm considering the possiblity of using a single Kokam 3270 on a Swift Racer that uses two 6V..."

Just checking... you mean 2x Kokams (to get you the 7.2v) in series?

Cheers,
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Old Dec 30, 2002, 01:50 PM
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rc-eflyer's Avatar
St. Louis, Missouri, United States
Joined May 2002
1,446 Posts
James,

Thanks for the numbers on the Kokams, those
look good

Norman,

I don't know what I was thinking with
just one Kokam. Of course it will take 2 so my
weight savings were just wishful thinking. So
batteries will weigh 128 gms which is about an
ounce heavier than the 720 Nimh. Like James
mentioned I might also have to get creative on
battery placement. I'll do some measuring and
report my findings.

Thanks guys
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Old Dec 31, 2002, 10:49 AM
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United States, NY, Spencerport
Joined Oct 2001
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How about using the 2050's instead?
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Old Dec 31, 2002, 02:56 PM
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rc-eflyer's Avatar
St. Louis, Missouri, United States
Joined May 2002
1,446 Posts
Quote:
Originally posted by mkirsch1
How about using the 2050's instead?
Not sure what 2050s are but I did see 2070s at
the FMA Direct site. These are 20gms lighter than
the 3270s which is the good news. The not so good
news is they are the same size as the 3270s (2.5" X
3.75") only thinner. This isn't going to fit in the
fuselage. Also they will have to strain a little
(about 4C) under full throttle.

What is your source for the 2050s?
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