"Larry" wrote

As alternator speed has NOTHING to do with its output once it's just off
idle, why not put the right pulley back on it, correcting the problem and
saving the alternator bearings from overspeed, themselves...premature
failure.

Spinning an alternator so fast DOESN'T make it put out another amp....

Look at any alternator output curve and you will see that amps increase as
RPM increases up to the point where they approach full output and then level
out. That point is usually between 2500 and 3500 shaft RPM. There are a
very few very expensive alternators, like the Eco-Tech, that are built to
produce close to full output at less than 2000 RPM that have a very steep
curve but most alternators require a minimum 2500 RPM to reach any
significant output.

That said, the OP's choice of alternators may not be the best if he wants to
charge at dead idle. The output curve has a particularly slow slope. He
should also consider that it takes a certain amount of power to produce 85
amps. Besides the output, the other item on that chart he should consider
is the Torque curve. When you use a pulley ratio that allows close to full
output at 800 engine RPM the torque increases to the point that invites belt
failure and excessive side loads on bearings.

His best option is to reduce the ratio closer to the original and charge at
1200 to 1500 engine RPM.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
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