Can an alternator be to big?
 

"Peter Albright" wrote in message
news:u2fvg.14644$A8.3191@trnddc02...
Glen,

Have you considered biasing the voltage sense line, to adjust the
regulator output voltage?

I have been thinking about that. Looks like that would be the only way to
control it. The internal regulator is set to maintain 14.4V on the sense
line. Boosting the sense line 1.2V would bring the output down to a safe
13.2V float. You could actually put a microprocessor to sense the battery
voltage and bias the alternator sense to do everything a "smart" regulator
does but that would be more work than I have time for.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

Can an alternator be to big?
 

Glenn Ashmore wrote:

"Paul Hovnanian P.E." wrote

Actually, the alternator will put out whatever the battery and loads
require. Unless you are charging a huge battery bank and/or have 200 A
load connected to it, it won't put out that much. Given the electrical
(and mechanical) losses, the input HP will be whatever are needed to
provide the electrical output. The larger alternator will have lower
electrical losses, but higher mechanical. All in all, this unit won't
present a mechanical load significantly different than a smaller
alternator.

That's just it. There will definitely be a heavy load on it. When it
cranks up every morning it will be seeing a 900AH battery bank ready to take
the first 225 amps in bulk mode.

This unit must be matched to the appropriate regulator. If you didn't
get one with the alternator, the deal may not have been that good.

It has the regulator built in. Pretty interesting one too. Even has a
battery voltage sense connection. However the regulator does not have a way
to change from bulk to absorption to float modes and there is no
equalization. The shore power charger can handle the equalization and with
my normal use pattern of 50% to 85% charge will rarely need float except at
the dock but it would be nice to have optomized bulk and absorption ability.

That could be a problem. If you could tweak the voltage setting down a
bit, you could slow down the battery charge rate and the resulting
engine load.

Petes's suggestion is pretty good. Put in some current sensing on the
gen. output and use that to bump the V sense line up as the generator
output approaches a setting suitable to your prime mover. You'll need a
gain control to set the V bias per amp load and set it so that the
system remains stable.

--
Paul Hovnanian
------------------------------------------------------------------
Have a pleasant Terran revolution.