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Watt's Up??????

Old 11-09-2008, 12:56 PM
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Join Date: Oct 2008
Posts: 61
Default Watt's Up??????

I finally broke down and bought a watts up wattmeter. Soldered Deans on it and tested it out. I have borrowed one at the field before to test a plane power output.
I understand how I use it to check the Amps of a plane under load to make sure I have a large enough ESC.
I also understand how to read the Peak Watts to get an understanding of the power being produced at WOT.
I know I am missing so much more that this can do and tell me
I have a variety of Lipos for a variety of planes I fly. Most all are 3 cell, 11.1V with various "C" ratings and Mah capcities.
1. How do I use my wattmeter to determine if my plane's power system is over taxing the battery???
2. How do I estimate flight times using this?
I have been to the website. I understand how this device works. Just want to learn more ways it can help me enjoy this hobby.
Thank You...
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Old 11-10-2008, 01:03 AM
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Join Date: May 2008
Location: PA. USA
Posts: 131

Ya need to take the readout numbers and start doing your ga-zin-tas.
(he-he, ya just gotta love Jethro from the Beverly Hillbillies TV show)

A 1500 mah batery is 1.5 amps because 1000 mah ga-zin-ta 1500 1.5 times. So if your pack is rated 20c it can handle a 30 amp load.If your pack is rated 15c it can handle 22.5 amps.
If you flew your plane drawing the full 30 amp load the full flight (which you should not do) you can expect a 3 minute flight time because flight time is determined by the capacity of the pack, times 60 than divide by the amp draw.

1.5 amps times 60 = 90, 90 divided by 30 amps = 3 minutes.

Also you can put your meter in line while charging your pack to see how much mah amps went in if your charger doesnt show that.
If I'm not making sense try this link for a start,

Last edited by CarpenterDave; 11-10-2008 at 01:25 AM.
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Old 11-11-2008, 03:22 PM
flypaper 2
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Location: Kingston Ont. Can.
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Biggest determining factor when all is done, is the prop. You can make or break your system with the wrong one. Motors are partly rated by the amp draw. say 20 amps steady. Then you'd pick an ESC a little over 20 amp, say 25 amp. Then pick batts. that can handle the 20 amps, say2200 ma. batt. At 10 C, that would be 22 amps steady. Now pick a prop that will make the motor draw just under the 20 amps, all shown on your wattmeter. Remember all these numbers are for full throttle running. Most flights are at 1/2 throttle except for hovering or aerobatics which is a small % of the flight. Hope this helps

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Old 11-11-2008, 10:05 PM
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Join Date: Oct 2008
Posts: 61

The more I use my wattmeter and get to know it, the more I like it.
Cannot imagine flying electric now without one!!
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