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Will brushless reduce Current?

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Old 02-24-2007, 12:51 PM
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LuckyEddie
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Default Will brushless reduce Current?

I have been trying to convert a Kyosho FV-1000 to Li-Po power. The aircraft comes with a brushed AP-29L motor in a 70mm fan and a 7 cell 1700-3000 nicd/nimh pack is recommended. The model simply did not fly with this set up, too heavy and underpowered, so I decided to try Li-po. I have put a 3s 2100 pack from graupner with current limit of 40A, with a 40A Esc. I thought this would work fine since current was 30A with the 8.4 volt NiMh. I was wrong! I measured the current at 40A with 3 or 4 clicks of throttle movement left! Obviously I could go with larger battery and esc, but I was wondering if fitting a more efficient brushless motor into the same setup should bring the current draw down?
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Old 02-26-2007, 12:13 AM
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Default RE: Will brushless reduce Current?

If the motor can handle the 3S lipo I would just go with a 50A brushed ESC.
Brushless motors in EDF units can be just as bad of an Amp hogs as are brushed motors.

However you may find that the smaller brushless motor will be just as powerfull as the heavier brushed, hence increasing your chance of succesfull flight.

You have to can probably find a brushless motor around 3800kV like a 450DF with a 35A-45A ESC

Best Wishes,

Dan
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Old 02-26-2007, 07:09 PM
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Default RE: Will brushless reduce Current?

Sorry! I don't agree with Dan on this one. First of all compared to a brushed motor the brushless will be more efficient than the brushed setup. The AP-29L will not be able to take 50 amps amps for reliable sustained flight. The motor will not be able to take over 3 cells without burning out so the best solution is a brushless motor.

Before we get into that. I would also look at the battery. The max that any 2100 cells can output is 15 C (this is assuming a battery from one of the major manufacturers). This means that you can only count on a max of 30 amps for sustained flight. This is probably not enough for a good hi power setup. I would consider switching to one of the 25C 2070 batteries from ThunderPower (or an equivalent Duralite, Hyperion, PolyRC, Polyquest, etc). This will give you a max of 50 amps for sustain flight and a high RPM because the voltage will stay higher under load.

For the motor I would find look at the Kv of the brushless motor that you are using now. I would then look for a motor of the same size in a brushless. Since you amp draw is now 30 amps. I would look for a motor with a kv of approx. 25% motre. This should get you up around 45 amps or so and with a resultant increase in power of close 50%.

Please keep in mind this is a calculated best guess.
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