"Roger Long" wrote in news:d%TQf.8372$Da7.541
@twister.nyroc.rr.com:

I have. Boiled those suckers half dry. It was the first boat I ever
sailed that even had a battery and I'd borrowed if for a long cruise
with a girl who was just a hell of a lot of fun to be with on a boat
and a great shipmate but turned out to the hound from hell back on
shore. But, I digress. I figured I'd better stop the bubbling and
let things cool down enough that I could touch the battery so I turned
off the battery switch.

That was not a WORKING regulator....That was a SHORTED regulator running
the field current at full maximum. The alternator was putting out over
21V open circuit and charging like hell!

Got back, bought my friend a new battery and alternator. A few days
later, I put in a new voltage regulator for him. A couple days later,
another alternator. Then another voltage regulator. The guy in the
marine store said, "Didn't I see you in here the other day? You
should always replace the voltage regulator and the alternator at the
same time. They're eating each other up." Everything was fine after
that but I'd run through about 75% of my net worth at the time. I
used up the rest flying down to Florida to try and convince that girl
to sail with me forever. That was a much bigger mistake than turning
off the battery switch while the engine was running!



The alternators were probably fine. Overcharging doesn't hurt them as
their inherent internal resistance limits their output current to a safe
level unless they are dead shorted, which usually burns the diode
rectifiers.

He was right about replacing the regulator with the alternator. That's
why you should use alternators with BUILT IN regulators....3 connections.
Power on - Ground - Battery. KISS is always the best...(c;

The series pass transistors in the regulator that regulate the field
winding overheat then short emitter to collector, effectively putting the
field winding directly across the battery terminals. This makes the
output voltage of the alternator go to maximum uncontrolled voltage. The
voltage causes heavy charging boiling the batteries (P=IxE - 16V x 80A =
1280 watts!) It melts the cases on some of the plastic batteries. Not
sure how much of this an uncooled AGM or Gelcell could take before it
explodes....They can't boil like a wetcell does, cooling the cell to the
boiling point.

Sorry about the girl....The battery was inconsequential in comparison...
(c;