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RogerN RogerN is offline
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Default Gas powered battery charger.


wrote in message news:d82ffccf-fad7-4a08-a367-
...

A good idea, BUT....work out how much motor power you would need to
get the alternator up to 70 amps...not a small motor....and coupling
it to the motor is no trivial matter either - but thats OK, no way
could you charge a battery at 70 amps anyway...let us know how you get
on, if you have the bits lying around then it would be fun - btw, you
would need to work out pulley ratios to get the alternator into its
power band without revving the motor to blazes - and some sort of
governor..(only if your obsessive...)

Andrew VK3BFA.


I was thinking about something like a 3hp Briggs & Stratton that already has
a governor. IIRC, those engines have a maximum RPM around 3600 so if I used
a pulley twice the diameter of the alternator pulley it would give me up to
7200 RPM on the alternator. All my autos that have tachometers show from
2000 to 2600 rpm at 60mph. The engine pulley looks (haven't measured yet)
to be 3 to 4 times the diameter of the alternator pulley. That would spin
the alternator maybe 6000 to 10,000 rpm. In my car when I have the lights
and heater on, at idle the lights dim and the fan slows, when I get over
about 1200 rpm things pick back up.

For experimenting, I could get a used lawn mower and cut the engine hole
pattern in a flat plate. Then cut holes for mounting the alternator and
install pulley and belt. It would be ideal if I could find a mower with a
deck flat enough to mount the alternator, kind of like a riding mower mount.

It would be nice to find a smaller lighter motor maybe perhaps a chainsaw
engine or good weed eater engine.

RogerN