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Old Feb 11, 2010, 11:27 PM
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bob_loblaw's Avatar
Antarctica
Joined Dec 2009
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4s on a 2-3s motor

Is putting 4s through a motor which states that it's for 2-3s a certain death sentence for the motor, or might it be fine if only used at WOT for very short bursts?

It's a suppo outrunner, so it's a decent motor with decent (and oiled) ball bearings.


Thanks.
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Old Feb 12, 2010, 12:22 AM
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Xpress..'s Avatar
United States, CA, Alpine
Joined Oct 2007
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Prop accordingly. The amps are what can kill a motor. If you prop down, then you should be fine
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Old Feb 12, 2010, 05:45 AM
Air, Ground & Water
freechip's Avatar
Canada, ON, Rockland
Joined Aug 2008
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Being decent and properly oiled will not help it if you are exceeding its limits.

If you are going to be using a higher voltage then rated then you should really invest in a watt/amp meter to see what is actualy happening.

Proping down is a must, by not doing so you could be almost doubling the amp draw and this could result in fried ESC and or motor or BOTH.
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Old Feb 12, 2010, 08:33 AM
Jack
USA, ME, Ellsworth
Joined May 2008
17,001 Posts
The watt meter is the key to figuring it all out. That and your fingers.

Use those on some 15 to 30 second static runs, checking the ESC and motor for heating as you do it. Stop the motor and use you fingers for the heat checks if nothing else is available. Too hot to keep you fingers on is 130F/53C, much hotter than that and you/'re headed for trouble.

The heat in the motor will be build in stator and the stator mount/base so feel the fixed part of the motor for heat, not the rotating part.

If your ESC has a linear BEC the extra voltage to drop the battery voltage to the 5V BEC voltage will be turned into heat too. So you'll probably feel a hot spot on one side of the ESC as it drops BEC voltage and then when you start running the motor the field of MOSFETs on the other side of the ESC will start heating up.

It is not too abnormal for the MOSFETs to get too hot to touch at full throttle but if the the temperature continues to climb it will eventually either lead to a overload shutdown (if you're lucky) or a fried ESC. Once you find the spot where the ESC does not exceed 160-180F or so you don't want to exceed that.

Jack
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Old Feb 12, 2010, 09:04 AM
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Canada, ON, Rockland
Joined Aug 2008
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heat test is good but you must understand that its based on what you feel is hot or not. My pain tolerance mite be different then yours but either way, if you are serouis about the hobby the a watt/meter will take the guessing out and you will be able to get the most out of the system.
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Old Feb 12, 2010, 08:38 PM
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Challenger 413's Avatar
Dickinson, Tx.
Joined Sep 2004
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Quote:
Originally Posted by bob_loblaw View Post
Is putting 4s through a motor which states that it's for 2-3s a certain death sentence for the motor, or might it be fine if only used at WOT for very short bursts?
As long as you prop/gear the motor for the higher voltage, you shouldn't have any problems. The main problem with using high voltage/low amps (HV/LA) is that, most will like the higher power and forget the throttle...

If you prop/gear the motor properly and use good judgement on the throttle, you should see more power and longer flight times.

Challenger413
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Old Feb 13, 2010, 02:33 AM
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Threshold's Avatar
London UK
Joined Jul 2004
2,530 Posts
I always though that a motor was wound for max efficiency for a certain number of cells. So if you use a higher count you are going to lose efficiency? So the best option if you want to use 4 cells is to get a 4 cell motor. Can anyone verify this?
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Old Feb 13, 2010, 10:43 AM
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MikeRx's Avatar
Dallas, Texas
Joined Dec 2009
2,190 Posts
Weight is my concern with high power setups but YEA, I'm doin 4cells on a E-Flight 300 motor that comes on the mini P-40. It draws 10.5amps peak around 140 watts with the included 7.2x5 prop..more than double the reccomended 2 cell power reccomended! Heat is NO issue. The setup is constucted of 2 Dualsky 25c 450mah 2cell batteries wired with a jst series harness through a Electrifly 12a controller (rated for 4 cells!) on a Great Planes Riot biplane. AUW is 9.3 oz, batteries and harness is 2.2 oz.

I have flown and tested back to back 2, 3, and 4 cells on 3 different 300 size motors with favorable results. Heat only begins to build when static testing and motor comes down plenty cool from flight. I think the current motor could handle 5 cells on the current prop for short bursts with cooling downlines.. BUT what small controller with LIGHT WEIGHT could handle the voltage?? IDEAS PLEASE?
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Old Feb 13, 2010, 10:45 AM
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MikeRx's Avatar
Dallas, Texas
Joined Dec 2009
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Quote:
Originally Posted by Threshold View Post
I always though that a motor was wound for max efficiency for a certain number of cells. So if you use a higher count you are going to lose efficiency? So the best option if you want to use 4 cells is to get a 4 cell motor. Can anyone verify this?
Depends on the amount of draw that is asked of a given motor...prop down and you will see MORE efficiency on many setups.
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