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Old 03-28-2011, 07:44 PM
  #11  
cliffh
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Join Date: Aug 2007
Location: Gustavus, Ohio
Posts: 686
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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??
Well I see that I have you confused. This stuff takes a while to understand.

Let me break your question down into a few parts.

"so if the ESC is the limiting factor" ---Well, the ESC may or may not be a limiting factor here. The ESC has a limit, in your case 45 amps. Voltage does not matter as long as you do not exceed the 4 cell limit. 500 watts at 11 volts would be 45 amps roughly. (11v x 45a = (almost)500 watts.

BUT, if you use a 4 cell (and maybe prop down a little bit) 500 watts at 14 volts would be 36 amps roughly. (14v x 36a = 500 watts (roughly)

The C-rating ONLY determines how much power the battery CAN supply, not WILL supply. It is a limit to NOT EXCEED only. Too low a C-rating can damage the battery, too high a C-rating...well, higher C rating batteries cost more and are a bit heavier.

Your ESC will NOT limit the current pulled. Your ESC is simply a very precisely timed switch that turns off/on the full power the system uses at full power. In other words, if "full throttle" is 43.35 amps...it switches that full 43.35 amps in pulses, closer together for high power, farther apart for lower power. Your ESC needs to be sized correctly for the FULL power requirements of your system. In your case, as long as full throttle is less than 45 amps (and you have reasonable cooling) you will be fine.

Your battery needs to be able to supply at least (preferably a bit more for a safety margin) the maximum amperage required at full throttle. In your case, at LEAST 45 amps continuous.

Your motor must also be rated for that 45 amps!

Your propeller will do the MOST to determine the power the system will attempt to draw. Nothing will determine the power (or amps drawn) than the propeller.

And last but not least, without a Wattmeter, you cannot tell how many amps your system is using. It is an important investment, along with a small selection of propellers.

In the mean time, maybe someone with a tested setup like you want to use can tell you what they are using.

Hope I didn't confuse you more

Cliff
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