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Amps, Watts & Motor out put!!!

Old 07-12-2015, 12:16 PM
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Ziet
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Cool Amps, Watts & Motor out put!!!

I have a Hacker A30x10XL and a 70A esc. On there web site it states 12x6 prop, 4s Lipo, X-55-SB-Pro esc. This setup has an out put of 696W so says the web site. However the power range of the motor is 650W. So why is there a differnce!

My setup is the same as the Hacker on the web site apart from having higher 70A esc. The out put is between 881/900W and 64A (watt meter tested) This is over the power of the motor.So do I use a smaller prop and why is there a difference please.

Any Help
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Old 07-12-2015, 01:40 PM
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birdDog
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I would certainly limit my current around the 42amps-15sec suggested by the manufacturer. They state 20-25deg timing.
I would prop down to get it within limits.
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Old 07-12-2015, 02:08 PM
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One other possibility. I'm not sure which website you are finding this on but somtimes sites list motors as 3-4s lipo, then they list prop sizes that cover the full voltage range.

"prop sizes 10x5 to 12x7" which covers both 3s and 4s. The larger diameter end of the spectrum dictating lower voltage while the higher voltage needing the smaller props.
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Old 07-12-2015, 02:57 PM
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JetPlaneFlyer
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On that motor 64A isn't a problem in my experience. Yes it's over the official Hacker limit but as long as you don't hold full power for long periods I'm 100% sure you will be fine. Current and power will drop off significantly once the freshly charged battery loses its initial burst of charge anyway, and drop again once you have some forward airspeed.

If it were mine I'd fly it as it is and just check the motor after flight to make sure it wasn't excessively hot.
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Old 07-14-2015, 02:27 PM
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Ziet
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Thanks to everybody for there helpful input
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Old 07-15-2015, 12:03 AM
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Wildflyer
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All 12x6 props are not the same. Unless you use the exact same type prop as they used in the test, you may and probably will get different results.

On a small foamie plane I had 11x7 props of different brands and types, that gave me wildly different power outputs. They ranged from 90 watts to 170 watts, with the same motor and battery.

Then also different batteries can give startling different results. On the same plane I was using above, which at the time all I could afford was a bottom line cheap 15C battery, I propped it to put out 170 watts, then later I bought a Hyperion 35C battery, the plane almost exploded. It was now putting out 270 watts ! Almost no voltage drop under load. I thought the voltage drop to be normal as it was my first electric plane, it was just a cheap battery.

Don't worry too much about 10-20% differences, when they get 50% too high then stop and check things. after awhile it all starts to make more sense. There are many things that can affect the readings.

Good luck, please come back with any questions you have.
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Old 07-27-2015, 07:44 PM
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Ziet
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I understand the importance of using a WATT Meter, but if the readings on the ground (static) are different to when the plane is flying, how do the two reading equate.
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Old 07-27-2015, 07:56 PM
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Originally Posted by Ziet View Post
I understand the importance of using a WATT Meter, but if the readings on the ground (static) are different to when the plane is flying, how do the two reading equate.

It's impossible to make hard and fast rules, but as a rough guide assume power in normal WOT flight will be at least 10% less than what you measure static with a 'fresh off the charger' battery.

As long as the motor is not getting too hot to hold after hard use, then you should be ok.
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Old 08-28-2015, 06:16 PM
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Ziet
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Again thanks for all your information and help
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Old 08-29-2015, 10:05 PM
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kyleservicetech
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Originally Posted by Ziet View Post
Again thanks for all your information and help
As Jetplaneflier indicates, if you can hold your fingers on your motor for 15 seconds immediately after landing without branding your self, it's running OK.
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Old 09-01-2015, 11:50 AM
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Originally Posted by Ziet View Post
I understand the importance of using a WATT Meter, but if the readings on the ground (static) are different to when the plane is flying, how do the two reading equate.
In general you don't want to have the motor running over its specs in the static test, on the ground. This will assure that you are not over specs in the air.

As noted by others, there is a certain "unloading" of the prop in the air because the plane can move. On the bench the prop can not move through the air so you get a little higher reading.

Wattmeters are there to help you insure you are not over the specs of the motor, ESC and battery, but it says nothing about cooling them in the plane.

If you do not provide adequate cooling air flow over the motor, ESC and battery and you overheat any of them the system will eventually fail.
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