On Sun, 8 Feb 2009 03:17:57 -0600, "RogerN" wrote:


I've been thinking about mounting an automotive alternator on a small
gasoline engine to make a portable battery charger with respectable output.
The purpose would be to charge auto batteries when there are no outlets
around. Of course you could do the same thing with a generator and battery
charger but I think you can get perhaps 70 amps or more from an alternator.
It would have been nice this winter when we had the ice & snow storm and the
battery was weak on the seldom driven 4WD diesel truck. Also could be
useful for camping and boating, could recharge the trolling motor battery on
the lake, etc...

RogerN


I did this about 20 years ago. Used a 3/12 HP Briggs engine and some
alternator that was given to me. No regulator though. I used a big
pulley on the engine to get the alternator spinning fast enough. I
supplied field current through a rheostat to get the desired voltage
at whatever load was on the thing at the time. If I was to do it again
I'd use a one wire GM alternator so that there would be good voltage
regulation. I had to reduce the field current manually as the battery
charged. I seem to remember that the 3/12 HP engine was underpowered
for the alternator I used which was (I think) a 35 amp unit.
ERS