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Old 03-28-2011, 08:07 PM
  #12  
dumo01
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Join Date: Mar 2009
Location: Columbus, Ohio
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Originally Posted by RCFlyer44 View Post
OK thanks guys, so if the ESC is the limiting factor here does that mean increasing my voltage and/or the C rating will NOT burn up the ESC but that the ESC will limit what current is pulled??
The current that is pulled will be determined by load you put on the motor.
The C rating indicates what the battery is capable of supplying without damaging the battery, it does not indicate that the battery will try to force more current though the system.
If you keep the power delivered by your system unchanged regardless of the input voltage, then the ESC will be OK using the P=IV principle. The motor speed will increase with the higher input voltage, so the only way to keep your power the same is to either prop down, in pitch or size, or limit the throttle you use. As noted before, the throttle down idea is limited by the way the ESC delivers energy.
Without knowing how much current the recommended 3s setup draws vs the 45 amp limit your ESC will support, it is tough to say if the 4s setup will over stress the ESC. The only way to know for sure is put a wattmeter on it, run it up gently and see what the numbers tell you as you run it up. I think the prevailing thought is to have at least a 10% buffer on ESC capacity vs actual current draw, so if you are at half throttle and drawing 40 a, then back off and get a bigger ESC ( overkill on the numbers but you get the idea). The alternative to a bigger ESC is to use a smaller prop, which, by turning at the 4S rate, whatever that is, may generate the same thrust as the bigger prop you used at 3S, and the plane may fly fine, but with a lower current draw so your ESC is OK.

Like Cliff said, you can kind of think of the ESC as a fuse, but not a fuse you can reset. When it pops it is dead, and if you are in the air, maybe the plane as well

Looks like I took long enough that Cliff beat me to it, but I think we are both saying the same thing.
They really are great toys, it just takes awhile to wrap your head around all the "buts" and "ifs"
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