Calling all you electrical aces!
I took the boat 60 nm north to have a hard top dodger installed.
When I left the home dock, the charging rate was 13.6 and doing well.
Several hours into the trip I noticed the charging rate was down and
dropping at 12.3. Ammeter showing zilch. Turned off all electrical with
no help and continued on in. Drove up a few days later to work on the
problem, but when I started the engine, all was normal. Good current and
voltage.
Picked up the boat a week later and same thing occurred. Worked good
for first few hours and gradually fell off.
This alternator uses a separate regulator. So it appears either the
alternator or the regulator is going south when it warms up.
So which is it or could it be something different?
Thanks
G

On Sun, 05 Apr 2009 18:09:56 +0100, Gordon wrote:

Calling all you electrical aces!
I took the boat 60 nm north to have a hard top dodger installed.
When I left the home dock, the charging rate was 13.6 and doing well.
Several hours into the trip I noticed the charging rate was down and
dropping at 12.3. Ammeter showing zilch. Turned off all electrical with
no help and continued on in. Drove up a few days later to work on the
problem, but when I started the engine, all was normal. Good current and
voltage.
Picked up the boat a week later and same thing occurred. Worked good
for first few hours and gradually fell off.
This alternator uses a separate regulator. So it appears either the
alternator or the regulator is going south when it warms up.
So which is it or could it be something different?
Thanks
G

Bad battery?

"Gordon" wrote in message
m...
Calling all you electrical aces!
I took the boat 60 nm north to have a hard top dodger installed.
When I left the home dock, the charging rate was 13.6 and doing well.
Several hours into the trip I noticed the charging rate was down and
dropping at 12.3. Ammeter showing zilch. Turned off all electrical with no
help and continued on in. Drove up a few days later to work on the
problem, but when I started the engine, all was normal. Good current and
voltage.
Picked up the boat a week later and same thing occurred. Worked good for
first few hours and gradually fell off.
This alternator uses a separate regulator. So it appears either the
alternator or the regulator is going south when it warms up.
So which is it or could it be something different?
Thanks
G

It just shows the regulator is working correctly.


Dennis.

Gordon wrote:
Calling all you electrical aces!
I took the boat 60 nm north to have a hard top dodger installed.
When I left the home dock, the charging rate was 13.6 and doing well.
Several hours into the trip I noticed the charging rate was down and
dropping at 12.3. Ammeter showing zilch. Turned off all electrical with
no help and continued on in. Drove up a few days later to work on the
problem, but when I started the engine, all was normal. Good current and
voltage.
Picked up the boat a week later and same thing occurred. Worked good
for first few hours and gradually fell off.
This alternator uses a separate regulator. So it appears either the
alternator or the regulator is going south when it warms up.
So which is it or could it be something different?
Thanks
G

It would help if you used proper terminology: "Charging Rate" should be
Amps, but it looks like you're giving us Volts. Both are useful, since
Voltage tells you what the regulator wants to see, and Amps tells you
how much energy is transmitted through the belt, out of the alternator,
and into the battery. Also, it would help to know what type/age of your
alternator, regulator, and battery bank.

I would normally expect an external regulator to either drop into "float
mode" after a while, which would be a bit under 14 Volts, or simply stay
at a fixed Voltage, perhaps about 14.2V. The fact that you never see
it that high sounds like you're not measuring at the battery, or have a
real problem.

In addition to the obvious regulator possibility, you might have a
slipping belt, which could appear to work when its cold, but then
essentially does nothing when it warms up and starts slipping. This
would usually fail the "sniff" test. You could also have a fried cable
to the battery - sometimes the end at the alternator can be charred
enough to fall apart when you wiggle it. This would appear as reduced
Voltage as the resistance wanders.

Gordon wrote in
m:

Calling all you electrical aces!
I took the boat 60 nm north to have a hard top dodger installed.
When I left the home dock, the charging rate was 13.6 and doing
well.
Several hours into the trip I noticed the charging rate was down and
dropping at 12.3. Ammeter showing zilch. Turned off all electrical
with
no help and continued on in. Drove up a few days later to work on the
problem, but when I started the engine, all was normal. Good current
and
voltage.
Picked up the boat a week later and same thing occurred. Worked good
for first few hours and gradually fell off.
This alternator uses a separate regulator. So it appears either the
alternator or the regulator is going south when it warms up.
So which is it or could it be something different?
Thanks
G


Swapping the regulator is the easiest test, but I think you're missing
just one diode in the 3-phase rectifier stack, intermittently, caused by
the diodes getting hot on a bad diode, the ones pressed into the heat
sink inside the alternator by the stators. If one diode opens, you get
one phase, instead of 3 and current goes way down, not keeping up with
the loads. The output with one diode open looks like this:

_____^_____^_____^_____^_____^ instead of a constant current output
caused by the phases overlapping each other. This will cause the radios
hooked to these batteries to whine at zero volume as the pulses of
current pulse the battery pretty hard because the regulator has the
rotor current running wide open trying to get up to its regulator
voltage.

Your regulator should float the charged batteries at 14.2 to 14.4 volts.
13.8 volts is the natural battery voltage at 1.260 specific gravity of
all the good cells. At 13.6, the battery will not top off....A full
battery will discharge a good bit to the 13.6V level. This is another
indication it's running on one phase....You get some charging current to
raise the battery voltage after starting but it falls off bad when the
load current exceeds the ability of the one phase to keep up with the
demands.

Take the alternator to Autozone or any car electric shop that has an
alternator test set. The best place is one that repairs diesel truck
electrics. He can test monsters like yours.

Your electrical loads may be exceeding the capabilities of the
intermittently rated cheap alternator on your boat. Skip completely
cooked a brand new alternator that WASN'T rated for CONTINUOUS DUTY on
Flying Pig from a electric dealer in Charleston. I found out from his
experience most alternators are INTERMITTENT duty, designed to recharge
starting batteries, not power full time electrical loads. Those
cheaper, open frame, car-type alternators are all intermittent duty.
They'll put out 120Amps....for 10 minutes before overheating....not 54
hours on a voyage. The current rating is simply the maximum current to
expect, PEAK CURRENT, not average.

Continuous Duty alternators, of course, COST SERIOUS MONEY. Look he

http://www.alphatrononline.com/Large...lternators.cfm

http://www.alphatrononline.com/image...p9-10_0811.pdf

Make SURE you're seated and leaning back against something solid when
they quote you the prices.....

On Sun, 05 Apr 2009 20:36:52 +0000, Larry wrote:

Your electrical loads may be exceeding the capabilities of the
intermittently rated cheap alternator on your boat. Skip completely
cooked a brand new alternator that WASN'T rated for CONTINUOUS DUTY on
Flying Pig from a electric dealer in Charleston. I found out from his
experience most alternators are INTERMITTENT duty, designed to recharge
starting batteries, not power full time electrical loads. Those
cheaper, open frame, car-type alternators are all intermittent duty.
They'll put out 120Amps....for 10 minutes before overheating....not 54
hours on a voyage. The current rating is simply the maximum current to
expect, PEAK CURRENT, not average.

For the better part of a century, big central station alternators have
been hydrogen cooled. Hydrogen is a significantly better conductor of
heat than air. I wonder how the price per Watt compares to small ones.

Casady

On Sun, 05 Apr 2009 20:36:52 +0000, Larry wrote:

Continuous Duty alternators, of course, COST SERIOUS MONEY. Look he

http://www.alphatrononline.com/Large...lternators.cfm

http://www.alphatrononline.com/image...p9-10_0811.pdf

Make SURE you're seated and leaning back against something solid when
they quote you the prices.....

Here's another possibility for a lot less money:

http://store.alternatorparts.com/d1-cs-144-dr250se.aspx

Diesel only, mount is a 2 inch Delco foot. The 250 amp model listed
above will put out about 150 amps continuously if driven by dual 1/2
inch belts.