Jim Woodward wrote:
Getting back to your original question.....

I don't think a bigger alternator is less efficent and it might be
more efficient, but I freely admit I'm speculating. Consider:

-- The bigger alternator will have bigger windings and therefore less
I^2 R loss inside. This is a small factor, as by far the biggest heat
producer in an alternator is the voltage drop across the output diodes
and that won't be affected. Nonetheless, it should be a plus for the
bigger unit.

-- The bigger alternator may have a bigger case and should therefore
run cooler, always a good thing.

I must add that I'm not quite sure why you ask the question, Glenn --
your various posts make it clear that you have an excellent
understanding of DC systems..... What do you think?

Jim Woodward
www.mvfintry.com

It is more a matter of balance. The immediate problem is that I
suddenly have a surplus of alternators. I was planning to use the big
270 amp hot rated Niehoff that I picked up off a fire engine that got
crushed by a falling wall. It needs about 10 HP at full output. It is
to be mounted off engine through a CV joint arangement to eliminate side
loads but when I add the Cat pump for the watermaker it runs the maximum
HP off the front of the engine up to about 12HP max. That is getting a
bit much even with the CV joint so when I got offered a 200 amp (cold
rated) Leece Neville fot $140 I bought it.

Now I am wondering which should be the primary and which the spare. For
all practical purposes the 750 amp bank is only going to take 175 amps
max and more like no more than 150 amps most of the time so the question
was will I be wasting enengy by swinging the heavier alternator? I
believe I agree with you that the answer is probably not. I think I
will mount the Niehoff and keep the LN in reserve.

--
Glenn Ashmore

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