Originally Posted by hayofstacks
Certain chargers will need a much larger power supply. I think its kyleservicetech that brings a gas generator setup he made to charge his li-ion battery packs in his larger models. He couldn't supply enough power with two deep cycle batteries to charge them.
Depending on the size of your model, the batteries that power the electric motor in the airplane can deliver significant horsepower levels. It's not hard these electric motors to exceed one horsepower output on a 60 inch wingspan acrobatic airplane.
Then, recharging the LiPo battery after a flight might take an hour or so, so the LiPo charger has to put out something on the order of 100 or 200 watts in this process. Again, 200 watts is over 1/4 horsepower.
The LiPo chargers are usually designed for a 12 Volt DC input voltage (some are rated to some 30 Volts DC). And, 200 watts at 12VDC is about 17 amperes.
To run these LiPo chargers, you need either a good quality deep cycle marine battery, or a 120 Volts AC to 12 Volts DC power supply (or power converter) rated for at least 20 Amps at 12 VDC.
(Yeah, I'm the guy that built up the gasoline engine/alternator setup. It's been working very well.)
This might put a little light on the subject for the larger electric models.
Thread on 70 size glow engine conversion to electric: (Check out "Field charging issues")
Typical power supply:
And, that DC alternator setup: