Jim Macklin wrote:
True, but a modern alternator will produce power at lower
rpm which means less drag. Also it should have lower frontal
area and internal cooling drag. Alternators don't need
heavy cast iron housings and w/o a commutator, should be
electrically quieter.

Ag planes often use a wind driven pump, so getting a proper
prop isn't difficult, just tell the prop shop how many watts
and what a/s, etc.

This one say 6 amps (yep, not much, but a lot more than nothing) at
85mph, weighs 5 lbs and is 5" diameter. Seven hundred bucks though...

http://www.aircraftspruce.com/catalo...s/turboalt.php

Let's see... a lot more expensive than another battery, but a lot
lighter too.