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Old Dec 09, 2012, 12:30 PM
Sure, I can fly after sunset!?
United States, MI, Novi
Joined Jan 2011
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Bench Testing

Sorry for the obvious question, but how do you use a wattmeter to bench test an electrical setup? I ran across related posts BEFORE I bought a wattmeter, but now I cannot find them!

I picked up an offbrand motor (EMP) and wattmeter at a swap meet, and want to test it before putting it on a plane.

I seem to remember something about limiting how long you run the motor, because the prop pulls a lot more watts on the bench than it does in the air. Don't want to burn up my power system. I assume you connect the wattmeter between the battery and ESC.

Do you first test the system without a prop on the motor, or will this damage the motor?
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Old Dec 09, 2012, 01:50 PM
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foamflyer's Avatar
United States, CA, Arcadia
Joined Nov 2003
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Meter goes between motor and ESC. Run motor with prop. It is true that prop will "unload" in the air.
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Old Dec 09, 2012, 02:51 PM
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jonone's Avatar
United Kingdom, Whitby
Joined Jun 2012
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Using a Watt Meter - FLITE TIP
Flite Test - Using a Watt Meter - FLITE TIP (10 min 9 sec)

wach this on utube. J.
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Old Dec 09, 2012, 03:05 PM
Sure, I can fly after sunset!?
United States, MI, Novi
Joined Jan 2011
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Quote:
Originally Posted by foamflyer View Post
Meter goes between motor and ESC. Run motor with prop. It is true that prop will "unload" in the air.
My wattmeter has two wires, but my motor has three. How do I connect between the two...any two wires?
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Old Dec 09, 2012, 03:34 PM
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United States, NM, Las Cruces
Joined Jul 2012
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You leave the motor wires where they are. You plug the battery into the battery side of the meter and the esc lead (where you would normally plug the battery) into the other. So it goes battery-meter-esc. Just solder on the connectors that match power system to the meter (unless it already comes with the ones you need).
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Old Dec 09, 2012, 04:28 PM
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JetPlaneFlyer's Avatar
Aberdeen
Joined Mar 2006
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The three wires go to the motor. The two wires that come out the opposite side of the ESC go to the battery. As you correctly said in your first post.. the wattmeter goes between ESC and battery (two wires)

PS.. running the motor without a prop wont do any harm at all. But you also wont get any meaningful readings from the wattmeter because without a prop there will be hardly any power being puled through the system.
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Old Dec 09, 2012, 05:14 PM
Sure, I can fly after sunset!?
United States, MI, Novi
Joined Jan 2011
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Thanks everyone.

Oh, and my other question: Is there a maximum time you should test the motor ... 30 seconds etc to prevent damage? Or does it matter as long as you're not exceeding the ESC and motor ratings?
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Old Dec 09, 2012, 05:45 PM
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United States, PA, Lansdale
Joined Feb 2012
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Hi mybad,
The amount of time you can run is determined by how much heat the ESC is creating. Since you may not get the normal air flow during a static test, you should monitor the ESC and motor temperature with some kind of meter.(IR or probe) Not your fingirs!!! Hope this helps. Heat is the enemy of the electrical componentes.
Frank Arbaugh
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Old Dec 09, 2012, 06:18 PM
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United States, AK, Fairbanks
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You should only run the motor as long as it takes for the numbers to stabilize so you can get a decent reading. Five to ten seconds usually does it.
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Old Dec 09, 2012, 07:42 PM
Reduce the drama...
rick.benjamin's Avatar
USA, OR, Damascus
Joined Apr 2004
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I agree with C4H10 (mooseberries mccoy) If you run it for any length of time,
you will notice changes as the battery begins to discharge.
This is normal, and as it is already a known fact, it's not useful information .
You're looking for watts and amps. That way you know if your over-loading your motor.
Take your readings, shut the test off.
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Last edited by rick.benjamin; Dec 09, 2012 at 07:45 PM. Reason: add pic
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Old Dec 10, 2012, 07:05 AM
Sure, I can fly after sunset!?
United States, MI, Novi
Joined Jan 2011
506 Posts
Thanks everyone!
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