Does this thing have a battery switch or are the batteries just
connected together in parallel? Battery switches should never be
moved with the engine running. Any alternator not hooked to a battery
puts out huge spikes of pulsating voltage that will destroy everything
in its path.

Just from what you've said, I'm leaning towards a loose battery cable
or a corroded one that puts resistance between the charging alternator
and the battery. The pulsating current of the alternator through
corrosion caused an extra voltage drop to add to the battery's natural
voltage, causing all kinds of trouble if the resistance it's pulsing
through is between the inverter and the battery posts, too. This is
why I always try to hook up electronics breaker panels to SEPARATE
terminals on the battery than the one the charging alternator uses so
these high voltage spike could only happen if the battery opened up,
as safe as I can make it.

High voltage spikes on all of it will occur, also, if the battery has
a dead cell in it, adding a big resistance right inside the battery
itself. You can hear a dead cell or corroded terminals on the boat's
AM/FM radio speaker. It shows up as alternator "whine" whos pitch
follows the RPM of the engine, of course.

Every boater should have a battery test meter. I paid $18 for mine
from Harbor Freight, a hardware discount place full of Chinese tools
made by slave labor. The test meter has an analog voltmeter and a
switched 50 amp load you switch on by holding the spring loaded switch
on. The meter is calibrated for unloaded charging voltages so you can
see what the battery voltage was before starting the engine, charging
voltage after the engine is running. Then, with the engine off, you
can load up the battery with the hot wire load in the box that gets
red hot to watch the battery's voltage discharge curve with the big
50A load for up to a minute to get an indication of its starting
capacity and plate integrity.

If the batteries are not "sealed", as many of the new ones are to
prevent you from just adding distilled water to them, rather than
swapping them out to make the battery store richer, you also need a
compensated hydrometer, which is identified by the thermometer built
into it to measure the electrolyte's temperature you've sucked up into
the glass. Cheap hydrometers are nearly useless as the specific
gravity you are trying to measure to see how the electrolyte is doing
varies WIDELY with temperature. A good hydrometer has a calibrating
chart so you can see what the gravity of the cells are at the
temperature on the thermometer....a correction chart for the float
reading. Of course, on these new gelcells and fancy Optima batteries
you're stuck with whatever happens in there.....at their mercy.

So, my guess until we get more information, is a corroded connection,
probably on the battery, itself, or a dead cell .......or, of course,
a shorted out field regulator.

How about some questions, now?

1 - Can you open the batteries to see what level the electrolyte is?
Batteries that are being overcharged gassify their electrolytes away
and need frequent distilled water injections to keep them from drying
up.

2 - Does the battery get too hot to touch while the engine is at
cruise speed? Overcharging makes them REALLY HOT. Normal charging
makes them warm, but not too hot to touch.

3 - Do you hear a high pitched whining in any electronics with a
speaker, even with the volume control set to zero? If there's
corrosion or a dead cell, the pulsating alternator, even a good one,
will make a whine in the speakers.

4 - Have you opened the battery caps and added distilled water high
enough to cover the lead plates? Manufacturers trying to make like
their batteries are "maintenance free", which is all bull**** to sell
batteries to naive people who don't need them, still have to have
removable tops, usually covering 3 cells at a time, that fit flush
with the battery top to hide them. They need that so the dealers can
open up the cells to add the electrolyte when they receive them from
storage dry. This gives them infinite shelf life stored dry. Pry up
these caps with a screwdriver and look into the cells. Buy gallon
jugs of DISTILLED WATER ONLY, not spring water or city water or hose
water (all of which contain calcium that will eat the electrolyte) and
fill the cells just up to the bottom of the filling cones down inside
the battery. Do NOT fill the cells to the top or you'll have acid all
over. If all the cells are dry and need lots of water....you HAVE the
overcharging problem you think you do. If all the cells but one need
water, the one that doesn't is 99% a DEAD CELL and the others are all
being overcharged by the regulator trying, in vain, to get the battery
to 14V when it only has 6 good cells....and needs immediate
replacement. The load meter will INSTANTLY find a battery with the
dead cell as soon as you put the 50A load on it. It'll drop 2V lower
than "normal" which is about 11.8-12.0V at 50A. (The meters are zoned
good/bad for this test so you don't have to remember that.)

After you initially start caring for them, check them monthly and
watch the electrolyte levels, which should all vary together. If
you're adding a lot of DISTILLED water to the cells month after
month....either the alternator is overcharging or you're leaving some
battery charger on way too long for good health. Modern batteries
hardly use any electrolyte in a year if they're being charged
properly.

Isn't boat maintenance fun?!......(c;



On 17 Aug 2003 06:36:11 -0700,
(Richard Malcolm) wrote:

I believe that my alternator is over charging. If this is so, I guess
that the regulator is not working right. here's my story. 93 four
winns/omc/ford/king cobra. one new 27 battery beginning of the season
the boat has 2. put in 1750 watt inverter this year. when engine is
running and on battery #2, the invertor reads that it is getting to
much power and shuts off, so I use it without the engine running or
when the switch is set to the other battery. 3 weeks ago the main fuse
(on the engine) popped while I was cruising. the voltage gage on the
dash read that I was chargining way to high until I reset the circuit
breaker. All seemed fine for a few weeks. yesterday, the main breaker
popped twice. I am going to take it to a pro if I can find one who has
the time to look at it. What else should I do or look for. hoping to
learn some as well as get the boat fixed. the boat has 2 gages to read
the batteries. one on the dash and one down below. I know that it
should be tested with external meters, but I do not know what or how,
but want to learn.

thanks


Larry W4CSC

Maybe we could get the power grid fixed if every politician
regulating the power companies wasn't on their payrolls.