"RoyJ" wrote in message
m...
I'm just finishing up a class demo unit that uses a 62 amp Motorcraft
alternator. I wasn't happy with the positive ground on that unit but was
cheap and had the external voltage regulator that I needed. 62 amps at 13
to 14 volts is around 850 watts. Calcs out to 1.15 HP theoretical. Any of
the 3 to 5 hp B&S, Tecumseh, import specials, etc should work fine at full
load.

To build what you are talking about, I'd get Delco alternator with the
internal voltage regulator. If you happen to have a used one, the rebuild
kits run about $15. Amperage varies considerably from a low of about 60
amps to around 135 on the units used on police cruisers. You probably
don't care, you don't really want to charge the battery much faster than
30 to 50 amps.

I have a Ford F350 with a 7.3L Diesel and 2 batteries. On a cold icy snowy
morning I decided to try to drive it to work (4X4) and the batteries were
too low to get it started. I charged it with my plug in charger but it took
a good while to get enough charge to start. I thought if I had a gas
powered alternator charger I could use it if I had trouble starting the
truck after work. I haven't tried one but I have doubts about those jump
starters being able to get the diesel running in cold weather.

Thanks for the information on the alternator, maybe I should select a pulley
to give 5000 alternator RPM at 3600 motor RPM, giving maximum alternator
output at maximum motor RPM.

RogerN

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