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Old Jul 23, 2012, 11:14 AM
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Not all battery ratings are all the seem....

The nano-tech 25-50c batteries I have perform a touch better than the standard 40C batteries because of the much lower internal resistance.

Smaller sized batteries, irrespecitve of their C rating, do not hold voltage well so their amp delivery capability is only for a few seconds after jamming the throttle all the way.
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Old Jul 23, 2012, 11:15 AM
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Australia, VIC, Melbourne
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If you use less C, then the battery is the part you will be killing, instead of the motor....
Horses for courses.
You need to use the RIGHT (adequate) battery, for the right (load capable) motor.
That is if you want a system that does its true best, AND will continue to do that long term - both battery and motor.

And the various battery 'qualities etc is why "Capable Amps" is a better number to show what they really can do. Not what the flakey C etc say they can do.
I use 2x as the multiplier that a battery needs to do a decent job in a setup - which means drive the motor as what it can do, and not damage the battery via excess load on it.
(but there are 100 and 1 one other factors that come into it all... but I start with the battery capability)
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Old Jul 23, 2012, 11:21 AM
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Oh, and those motors fried in a twin 70mm using that battery.
So that was 55A each at WOT = 110A and the "174A capable" battery is only marginally up to that job (seeing I say you want 2x the current needs to have good leeway), but at the weight level the battery was, I chose to use that rather than a heavier more adequate battery - at the expense of its harder life, which would mean shorter life overall.
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Old Jul 23, 2012, 11:23 AM
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Originally Posted by airraptor View Post
EXT did you cut the overall length of the blades or the cord?

Also guys i am not tryingto get max power out of these fans, if wanted to do that i would just order a setup from EXT. As i stated earlier these will go in some FREE GWS 262's I have. looking for low power set up with somewhat of a whoosh sound. now if there was a 64mm version it would be simple.
Maybe you can get a pair of Mercury 64mm from the King. Not s cheap as the CS though.
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Old Jul 23, 2012, 11:24 AM
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Originally Posted by PeterVRC View Post
If you use less C, then the battery is the part you will be killing, instead of the motor....
40c at 2800mah = 120-ish amps constant ....the 2100kv motor will pull 60-ish amps on 6s no?

That's half the C rating for a 2800mah pack WOT...

That extra half to full volt makes a tangible difference on the operation of these motors it seems. For 12usd to 16usd for these motors I'm not going to complain

No head room = 40c and below for me...I don't mind...40c packs these days are still decent quality and I'm not trying to fly past 90% capacity
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Old Jul 23, 2012, 11:26 AM
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Originally Posted by PeterVRC View Post
Oh, and those motors fried in a twin 70mm using that battery.
So that was 55A each at WOT = 110A and the "174A capable" battery is only marginally up to that job (seeing I say you want 2x the current needs to have good leeway), but at the weight level the battery was, I chose to use that rather than a heavier more adequate battery - at the expense of its harder life, which would mean shorter life overall.
What's the burst current on the pack?

Regards
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Old Jul 23, 2012, 02:05 PM
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........
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Old Jul 23, 2012, 05:30 PM
speeddemon
United States, TX, Whitesboro
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if saying to high of a C rating is bad then what would be good for a 3000kv motor with a 100amp esc?
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Old Jul 23, 2012, 06:18 PM
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So is there any housing that the Turnigy SK3 will easily fit in? It sure doesn't go into the CS10 housing.
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Old Jul 24, 2012, 12:51 AM
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Originally Posted by SteveC68 View Post
So is there any housing that the Turnigy SK3 will easily fit in? It sure doesn't go into the CS10 housing.
Steve,

which SK3 the 3300kv on a stand-off?

It does fit!....

You just have to inset the ring at an angle and then work it in. Fits like a glove.
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Old Jul 24, 2012, 03:25 AM
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I have an SK3 I have never used.... hmmmmm......
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Old Jul 24, 2012, 03:26 AM
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Well I don't think "Burst" stands for much of use either.
The best way to know the true ability is test it in the combo. Then you will find out what is sustainable, and what a 'burst' can do too.
And it is never anywhere near what the crap numbers say!! So that is a waste of time worrying about those.
(it is a 30C - 40C battery)

My quoted numbers were 'sustainable'. eg the L2855-2100 did 58Amps sustainable on the battery. 67Amps for peaks (eg rest it and burst again etc). That is 1400W peaks.

If you use a 6S battery that CAN'T do that, then you are overtaxing it and will shorten its lifespan (cycles). Because even though it can't do it, it will be TRYING to. And will run hotter, and if you do it too much it will damage it (strip anode?).
Same as running a battery down too low. Same principle occurs - just relative to how much over-stress you are doing to it.
So you should never be using a battery that is not up to what the load truly wants. You should have a lower kv motor to correct that properly. Or... a better battery.
(there is sort of a circle of 'wants more amps, volts drop, less amps then'... what came first, the chicken or the egg?.... it stabilises volts/amps somewhere.... but overall it is overloading the battery)
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Old Jul 24, 2012, 03:31 AM
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Originally Posted by PeterVRC View Post
I have an SK3 I have never used.... hmmmmm......

Try it. Just make sure it never spins for long pulling more than 85amps.... or it will do what your 2100kvs did.... I am tempted to try another one but only in a plane of fully unrestricted intakes.. like an ME-262 or an SU-35.

But then again why do that the L2855-2300kv on 5S does better....
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Old Jul 24, 2012, 03:41 AM
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Yep, the L2855-2300kv is a killer combo. So if that suits, that is best.

I am not sure what I would use the SK3 for.... was it 3300kv? Too much for even 3S really.
It pretty well has to go into a 5 or 6 blade 3S combo. Which was propbably what I bought it for originally. But I hate 3S 70mm EDF's, LOL. Even 4S.
I don't want to see less than 5S for 70mm's! (though I have a painful F-15 4S CS10.....)
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Old Jul 24, 2012, 03:49 AM
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The SK3-3300kv would do very well in a Wemo on 4S. Just as long as amps are kept down to a max of around 80A.
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