-=> George White said to Greg Mayman
 -=> about "VEHICLE LED'S" on 09-27-03  08:20.....

 GW> We are, in general :-). However I've spent over 10 years in automotive
 GW> electronics design working for CAV (as it was know then), including
 GW> work on their 440 regulator (I still have some in the loft!). I also
 GW> have a degree that majored on semiconductor physics (though it is 30
 GW> years ago now, I don't think the basic physics has changed).

Good for you!

 GW> That "near full" is probably 99% of full and most people
would never
 GW> notice the difference. However, nit picking, I only said "the
 GW> batteries are never fully charged" for an alternator sensed system.

Again, it is a matter of defining what is meant by "fully
charged".

 GW> When I worked on the CAV 440 regulator it had a choice of 3 settings,
 GW> from memory 12.5 (for NiCad systems), 13.5 (normal) and 14.5 (for
 GW> heavy use/cold climate).

So for lead/acid batteries, in a halfway cold climate or for
medium heavy use the alternator could be set to 13.5 which would
leave the battery undercharged, or to 14.5 which would overcharge
it.

And did the charging system cut out completely at this voltage or
was it the point at which charge would be reduced to something
approximating a trickle charge.

And was this an exact voltage, under all conditions, or a nominal
figure?

And when the vehicle was used with a fairly substantial drain
from lights etc, say 200w (about 16A), which would cause an
appreciable voltage drop in the wiring, was this compensated for
in the regulation of the alternator? In other words, did the
regulator control the voltage at the output of the alternator or
at the battery terminals?

In truth, it's all a compromise.

 GW> Indeed true, however there is _always_ some volt drop, and of course
 GW> the lower the current, the lower the temperature rise within the
 GW> diode, so there is a balance...

Correct.

 GW> From the manufacturers point of view it stops people who don't know
 GW> better setting things up wrongly and then having problems when they
 GW> kill batteries through overcharging or their engines won't start in
 GW> cold weather because the batteries are undercharged and then blaming
 GW> the manufacturer for the problem (and sueing them in these litigious
 GW> times).

Yes, that is very true. While it is always better that any system
be re-adjusted correctly for changing conditions, it is also
axiomatic that any adjustments be kept well away from
well-meaning but often uninformed tinkerers.

We all know of the nail in the fuse holder.

 GW> Unfortunately true. However I have a reasonable collection of old data
 GW> books to hand... :-)

So do I, but all to often not the ones I want or need. And most
of them are much too old to tell me anything about components in
stuff that is currently going "out of date".

 GW> We're agreed then :-).

Of course ;-)

From Greg Mayman, in beautiful Adelaide, South Australia
   "Queen City of The South"    34:55 S  138:36 E

... Many are called, few are chosen.  Fewer still get to do the choosing.
___ Blue Wave/386 v2.30

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