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Old Jul 27, 2005, 03:20 PM
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WOT or NOT?


I just hooked up my new Medusa power analyzer to my formosa with an Aurora 400T, 17A spd control, Kokam 3s1p 1500 10C lipo, GWS 8040 DD prop, and it read 6.5 amps and about 69 watts WOT?? The specs on several websites including motocalc have this setup at about 10 amps and closer to 100 watts? I don't get it. I even checked the EPA on my Optic 6 for the throttle channel and moved it up to 125%. It just doesn't seem to be running wide open! Maybe a problem with the speed control? It is an ELE, but it appears to work flawlessly. Any ideas?

Brett
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Old Jul 27, 2005, 04:08 PM
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What was the voltage? If the battery sags then the current will drop also.
Old Jul 27, 2005, 04:19 PM
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The battery was fresh @ 12.6 volts.
Old Jul 27, 2005, 06:02 PM
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The 12.6 volts is a fully charged pack with no current being drawn. What is the voltage shown by your Power Analyzer while running at full throttle?
Old Jul 28, 2005, 01:56 AM
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It was around 11.4 to 11.6 I believe. I also found that when I changed around the motor wires and the motor reversed, I was getting up around 8 amps at closer to 80 watts. I have the GWS prop with the lettering facing outward.
Old Jul 28, 2005, 09:55 AM
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Ok, I just ran it again and the battery was down to 11.8 V.
At WOT voltage dropped to 10.4 (down 1.4 V). That seems like alot! So is this a battery related problem?

Brett
Old Jul 28, 2005, 10:01 AM
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It could be related to the thinner air you have up there in Colorodo Springs. Thinner air lets the prop spin faster unloading the motor.
Old Jul 28, 2005, 10:13 AM
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Well if thinner air is all it is, than I should be able to "prop up" to get more power out of this thing. I am not pushing the motor, speed control, or battery even close to its max power ratings. I'll have to pick up some different props...maybe a 9x6 or 9x7 and see what kind of draw I get. I should have put that in my specs. I fly at 6400 ft! I knew it would make a difference, but I didn't think it would be that much! Thanks for the help.

Brett
Old Jul 28, 2005, 11:04 AM
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A tachometer would tell the story. If it is spinning faster than predicted, then the current will be lower. If slower, then you still have a problem.

Make sure you have the right connectors. At this current, JST will not cut it. I use the Deans connectors on my TREX. It hovers at 10 amps.
Old Jul 28, 2005, 08:50 PM
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I'm using Deans connectors and the motor wires I soldered on are thicker in guage than what came with the motor. I'm pretty sure I have all the bases covered. I'll pick up some other props and give it a try. Thanks again.

Brett
Old Jul 29, 2005, 12:19 AM
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Altitude can make a very big difference. 6500ft. vs. sea level is a huge difference. I'd try a GWS 9X5 HD; i expect that'll give you the numbers you expected.
Old Jul 29, 2005, 01:04 AM
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I agree with the above guys about altitude effects. One thing I thought I would mention that hasn't been said concerns Motocalc predicitions. I find on all my brushless setups that Motocalc consistently predicts around 2 amps less than my wattmeter shows is actually happening. I have not been able to find out a valid reason...and this is true on 5 different brushless motors, battery packs, speed controls, etc. Very consistent 2 amp low?! Just something to consider checking.
Ken
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Old Jul 29, 2005, 12:05 PM
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Excellent, thanks for the feedback guys!


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