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Old May 07, 2012, 01:45 AM
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What the smallest AWG you have used from ESC to motors

I am building one of the standard tricopters that "everybody" makes. I use 10mm alu-tubes and I will have the cables from the ESCs to the motors inside the tubes. 16 AWG, which I normally use, is to thick to fit so I might go for 18 or even 20 AWG.

Has any of you tried using that thin cables on your multicopters from ESC to motor? How did it go.

I dont want theory here, because that will tell me 18 and 20 is too thin anyway. I want real world experiences. Is it really that bad to use this thin cables?
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Old May 07, 2012, 01:51 AM
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what size esc and motors are you using? what does the esc have on it?
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Old May 07, 2012, 01:56 AM
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Its Epp 1045 props and rctimer 2836.11 motors, 750 kv. The ESC are Turnigy plush 18 amp.
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Old May 07, 2012, 02:04 AM
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interesting question I was wondering the same. my nx4008 motors have 20awg wires going into the motor which is smaller then the wire coming from my esc. I was going to desolder the wires coming from my escs and use 20awg all the way. anyone see this being a problem?
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Old May 07, 2012, 03:16 AM
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The big question is how long do you plan to run the wires? Your motors are small enough that 18 gauge should be ok of the run is not too long. You may even use 20 gauge. The problem will be voltage drop from the resistance which will create heat.
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Old May 07, 2012, 04:46 AM
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Originally Posted by SeismicCWave View Post
The big question is how long do you plan to run the wires? Your motors are small enough that 18 gauge should be ok of the run is not too long. You may even use 20 gauge. The problem will be voltage drop from the resistance which will create heat.
I am also interested in hearing experiences from those who has actually tried using thin cables. Out of that I can try to compare their setup with mine. Your post was very helpful though, and I welcome more of those too.

There is so much theory out there that calims you need as thick cables as possible, but does that correspond to the real world. Has anyone actually had big problems using 18 or 20 AWG? I want to hear both good and bad experiences regarding 18 and 20 AWG. Both long and short cable stretches.

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Old May 07, 2012, 07:37 PM
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Lets say I had a continuous drag at 12 a from ESC to motors. The strech is 60 cm.
Would that be to much for 20awg?
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Old May 07, 2012, 07:56 PM
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Im using 20awg wires with Turnigy D2836-11 750KV motors and 30A ESC's for 20cm. So far no heat, loss of power or anything in that area. But make sure it's a good quality cable.
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Old May 09, 2012, 10:33 PM
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My original Tri has 2836-11 with RCtimer 18A. It has 20ga from the ESC to (motor wire), 8" total ,and 20ga from the ESC to battery, 6" total. This model has well over 200 flights with no problems.

I think you will find the small loss in the 20ga wire counters the weight of bigger wire.

Mine hovers at 4-5 amps per motor, the motors very seldom "see" full power.
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Old May 10, 2012, 10:25 AM
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it is all about length and voltage drop. (which translate to heat) 12" length of 20ga at 20 amp will see a .418 Volt drop at 12volt. about 8 watt of heat on the wire. enough to heat it up good. 20ga wire has 11 amp rating for chassis wiring, but for really short length and burst power, you can get away with bit more than 11 amp.



here is a calculator and spec sheet

http://www.powerstream.com/Wire_Size.htm
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Old May 12, 2012, 04:36 AM
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Ok thanks for the tips. My stretch is pretty long, its about 1.7" from ESC to motor. The leads have a silver color so I dont think it is copper so I dont know what to fill out in the calculator you mentioned.
Anyway, I guess maybe it was a mistake to go for 20AWG which I have now done. Do you have any idea how much this will affect the flight-time. I mean does it sink proportionally with the voltage-drop or does it drop more? For example, will a 5% drop in voltage lead to a 5% drop in flight-time, or does it drop less or more?

How do I measure the voltage at the end of the cable? I mean, there are 3 wires there. I have got the classic meter that the electricians got to measure with.
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Old May 12, 2012, 04:59 AM
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Originally Posted by babanan View Post
How do I measure the voltage at the end of the cable? I mean, there are 3 wires there. I have got the classic meter that the electricians got to measure with.
You just need to measure 1-wire.
To measure the voltage drop will require a siginificant current to be put through the wire.
For 20AWG, the cable has a resistance of ~33mOhms/metre.
Simple Ohms law says V=IxR
so putting 10amps will result in a voltage drop of 0.033 x 10 = 0.33Volts across the wire

Now quite how you go about putting 10amps thru the wire .....
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