"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;

"Larry" wrote

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

Well, it was a long, long, time ago in a galaxy far, far away.

You brought up a good point though. A similar failure would spray
acid soaked fiberglass mat all over my engine room. Since I don't
have an engineer standing watch to keep an eye on voltages, what would
you suggest for a simple alarm to let me know that things were
starting to go to hell in a handbasket in the voltage department?
Would you try to trip on overvoltage or just measure battery case
temperature directly?

Oh yeah, the other girl I sailed with in that boat:

We went swimming in Edgartown harbor straight out of the bunk if you
know what I mean. I got the sail up on the cat boat and we sailed out
just as we came off the assembly line. It was race week and the fleet
caught up with us and passed us motoring out to the starting line. A
yawl from the Naval Academy passed close along side. Suddenly,
someone barked an order and the entire crew lined the rail, snapped to
attention, and saluted.

There is nothing, absolutely nothing, half so worthwhile as simply
messing around in boats.

--

Roger Long

"Roger Long" wrote in news:z3oRf.1554$Mj.799
@twister.nyroc.rr.com:

Would you try to trip on overvoltage or just measure battery case
temperature directly?



A voltmeter to watch that is accurate. By the time the temperature
sensor were to alarm the battery was too hot, it would be too late.

You have a long time notice the voltmeter is too high, however, as its
reading is instantaneous. Just mount it next to the oil pressure guage I
hope you're monitoring when the engine is running, not waiting for the
oil pressure alarm to tell you the crank doesn't have any lube and it's
too late to save it.

Just like in my car and truck, I want those guages to be right in front
of me when the engine is running, not some idiot light that comes on too
late. I want to see what the oil pressure and charging voltage is doing.
As to the charging, the Link 10:
http://www.energyoutfitters.com/prod...ntrex_link10.s
htm
is my guage of choice. Not only does it monitor the charging with the
alternator, but it monitors the discharging and AC battery charger's
progress, as well. Every boat with house batteries should be using one.
You can monitor your charging voltage and current, as well as your
discharge current and available amp-hours to plan how long you can run
them down before safely recharging....not waiting until the lights are
too dim...(c;