| You are thinking of the old fashioned motor /speed controllers where | they used a resistor. Today's modern units employ switching the | turns the power on and off at a high rate, not much heating involved | in this process.
Well, what he said is still correct about a brushed ESC -- it's most efficient at 100% throttle, and less efficient at lower settings. Of course, the difference is like 99% vs 95% or so -- not very signifigant.
Brushless ESCs are always switching, even at full throttle, so I wouldn't expect them to become more efficient at 100% throttle. One reason for going brushless is that things overall tend to be more efficient at partial throttle values than brushed systems, however.
That's the key right there ... `commensurate with desired performance'.
You may be right -- a motor+ESC might be most efficient at 100% throttle (they often are, especially for brushed systems.) But if you need 100% throttle to fly around, then that doesn't leave you much extra power for playing around, and if your plane isn't fun to fly, why bother?
| > and run it at full power rather than installing a big motor and | > running it at part throttle?
If you're looking to break a world duration record, absolutely. If you're looking to just fly around and have fun, maybe not.
Also, that bigger motor weighs more, and that alone will make the plane require more power to stay airborne.
If you're really interested in maximizing power system (battery+ESC+motor) efficiency, get the `Electric Motor Handbook' by Robert Boucher.
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Looks like it's been discontinued, so it might be hard to find.
It's a bit dated (for example, brushless motors only get a paragraph or two, though most of the rest of the book applies to them too) but it does a pretty good job of explaining things. It's also really `dry' -- Boucher doesn't seem to be the best writer, but he does know his stuff.