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Motor shuts down moments after throttling up.

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Old 01-17-2011, 06:31 PM
  #1
linelizzard
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Default Motor shuts down moments after throttling up.

My neighbor just got an RTF for Christmas with a Spectrum DX7 TX. His little plane binds ok, but as soon as he throttles up, the motor shuts down. The battery checks out ok. Could this be a factory bad esc?
I don't have any more info on this little plane. We were just "talking over the fence" today.
If anyone has had this problem and found a "fix" I would appriciate the input.
Thanks
L.
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Old 01-17-2011, 06:45 PM
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Default RE: Motor shuts down moments after throttling up.

More often than not, the battery turns out to be discharged or defective. When you say "the battery checks out OK" what do you mean? If you test the battery with a voltmeter and it shows xxx.x volts that does not really mean anything. Yoiu must check the battery under the same load as the motor/esc combination. For example, if the motor draws 10 amps when running at full throttle, then you must check the battery under a 10 amp load and see how many volts it is producing at that load. Most of us don't have the test equipment to do this.

Of course, you may be right the ESC may be bad or configured wrong. But in my experience, it is usually the battery.
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Old 01-17-2011, 06:51 PM
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Default RE: Motor shuts down moments after throttling up.

I have been flying Electric RC for some time now.

When you Throttle up and the ESC shuts down the motor, it is usually because you are pulling more Current (amps) than the ESC is rated for. I have seen this many times.

Buy or borrow a Wattmeter. This device is connected between the ESC and the Battery. It will tell you how much Voltage, Current, and Wattage you are using. You can put a smaller prop on the aircraft until, at full throttle, you are not drawing more current than the Motor, ESC, or Batteries are rated for.

Check the specs on the Motor, ESC, and Batteries. You need to have the correct Voltage batteries. The Capacity (C) of the batteries determines how long you can run the motor. The batteries will be rated for how much current you can draw Continuously, and in a Burst. If, for example, the battery capacity is 2500mah and the battery is rated at 20C, you can draw a maximum of 5 amps (5000 milliamp hours) Continuously. If you system draws more than that, it will shut down or you may damage the batteries. The ESC will shut down the motor if you draw more current than it is rated for. If the voltage is too high, you can damage the ESC or the Motor. If you are using LiPo batteries, 2cell is 7.4 volts nominal and 8.2 volts fully charged (3.7v per cell), as an example.

Reduce the Voltage or Current Draw or lessen the Load on the system by reducing the Diameter or Pitch of the prop and your Throttle should work normally. If the ESC is defective, that might also cause it to shut off under load.
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Old 01-17-2011, 09:49 PM
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Default RE: Motor shuts down moments after throttling up.

I went over to the neighbor's and took a new esc and battery to check against his equipment. As it turned out, his esc doesn't seem to work correctly. When I powered up with my new battery I got the same outcome as before. I switched the esc and everything works great. On his esc, all the motor would do is come on and run at about 1/4 speed and in about 5 seconds would shut off. It wouldn't change RPM no matter where the throttle control was moved. I tried several times to reprogram it but it just continued to do the same thing. I advised him to take it back and ask for a replacement.
Thanks for the help.
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Old 01-18-2011, 04:42 AM
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Default RE: Motor shuts down moments after throttling up.

The little Bind nFly models which use higher output motors can easily suffer from the "throttle up n die " condition.
TheVAPORS don't
The UMC300 's do
The difference lies in higher current drain. Years back -my first electrics -runing horrible LiPos on the little geared electrics from GWS all suffered from the overload problem- you had to carefully match prop sizes (load) to motor- esc and batteries
Things are much better now but the problem will always exist in electrics -if the battery is undercapacity -or the prop load is excessive.
Also watch for any drag in the output shaft on the little geared stuff - - a hard bump may cause drag in this area and th e battery will quickly run down.
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Old 01-18-2011, 05:22 AM
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Default RE: Motor shuts down moments after throttling up.

line - I am glad that you are taking action to have the equipment checked by a technician.

As I mentioned, above, if you are going to fly electrics, a Wattmeter is a MUST tool. You can get them at your LHS or via mailorder. It is not expensive. Also, read the specs on the motor, esc, bec, and batteries you intend to buy so you know you have the right components. There are free calculators, like Motocalc, that let you plug in the numbers for each component to see if they are right for your model. It is somewhat easier, now, to translate a Glow or Gas motor size into it's electric equivalent, but you still need to do homework.
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Old 01-19-2011, 06:42 PM
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Default RE: Motor shuts down moments after throttling up.

Sorry!! I meant 50amps or 50000ma draw at 20C.
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