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Old May 22, 2010, 11:52 PM
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Joined May 2010
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Help!
Need help going for 14.8v!

Hi guys I'm new here.
I've brought a 4s lipo for my fpv plane which was previously running under 3s
the motor's kv is 1400

What Adjustment should I make to have the best efficiency out of it?

Could I simply change the propeller from 8 inches to a smaller one, like 6?
Or do I have to buy another 1000kv motor and keep the other setting?
Which solution is better? Smaller propellers seem to have a lower efficiency on a heavy fpv plane.
I'm going for the 1st because I might also run it under 3s, changing propellers is much easier...

Thanks!

Edward
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Old May 23, 2010, 08:09 AM
An itch?. Scratch build.
eflightray's Avatar
South Wales U.K.
Joined Mar 2003
13,801 Posts
The safest way is to use a wattmeter, (or just an ammeter), to make sure you are not overloading the system.

But, yes changing the propeller to keep the amps down, if increasing volts, or going to a larger prop if reducing the volts, is perfectly Ok.

You don't need to change the motor, BUT, check the ESC is Ok with 4s. Some, (make that most), ESC's limit the BEC side to 3s, as 4s can overload the voltage regulator.
You may find to go 4s, you will need a separate BEC/UBEC or 4.8v pack, and have to disconnect the ESC's red wire at the connector, (3 wire Rx connector).
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Old May 23, 2010, 12:52 PM
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Thanks for the reply. about the BEC, Can I just put some diodes (maybe 3)before my bec to step the volt down a bit?
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Old May 23, 2010, 02:40 PM
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Staffs, UK
Joined Nov 2003
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Quote:
Originally Posted by sklsy View Post
Thanks for the reply. about the BEC, Can I just put some diodes (maybe 3)before my bec to step the volt down a bit?
No you almost certainly can't. The BEC is a circuit which is built into your ESC. You'd need to be able to modify the complex printed circuit it's built on.

Steve
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Old May 24, 2010, 04:09 AM
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Originally Posted by slipstick View Post
No you almost certainly can't. The BEC is a circuit which is built into your ESC. You'd need to be able to modify the complex printed circuit it's built on.

Steve
My bec is a ubec which is a seprate part from the esc.

Will it work then?
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Old May 24, 2010, 05:11 AM
An itch?. Scratch build.
eflightray's Avatar
South Wales U.K.
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13,801 Posts
Yes, just check the ubec's rating if your not too sure, but most ubec are rated to at least 6s.
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Old May 24, 2010, 08:44 AM
I think I forgot how to fly RC
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United States, WA, Woodinville
Joined Mar 2007
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Quote:
Originally Posted by sklsy View Post
Thanks for the reply. about the BEC, Can I just put some diodes (maybe 3)before my bec to step the volt down a bit?
why would you want to step the voltage down a bit for the Ubec?

As the other fella mentioned, ubec's are typically rated for 6s operation, unless its more of a voltage regulator that is specifically listed as 2s input such as the turnigy Megabec 8.

If its a turnigy 5a ubec, its a switchmode ubec and rated for 6s max input.

specifics of your hardware is always very helpfull if you wish to receive good advice.
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