ray lunder wrote in
:

Anyone have any experience with
this type of thing?
Also, the fan is sucking air from the front of the pulley and blowing
it through the body and out the rectifier end towards the stern. Is
this correct? The cowling is pretty close to the front of the engine
so I don't see how it's going to get much ventilation. Thanks as
always.


Any charging system must have a series resistance to limit charging
current on initial charge. This resistance drops the excess voltage
between the battery's voltage at whatever state of charge it's in, what
the voltmeter in the dash reads, and the charger's natural design
voltage, which is around 18 volts for 12V alternators to make the
charging stable up to 15VDC, giving the regulator something to control.
(Your solar panel chargers run 18V loaded to spec and up to 28V sitting
in the sun totally unloaded. Their internal resistor is the silicon
cells, themselves, which get really hot at full load current.) In an
alternator, it's the resistance of the windings in the stator, in series
with the load current as they are the source of that current, that are
designed to be the series resistance of the charger. (The transformer
windings of an AC battery charger is the resistor in them as well as the
selenium rectifiers in old chargers.)

All this designed-in series resistance gets HOT (P=IxE) when there's lots
of I, the charging current. So, to cool this resistance, the alternator
has an open case with a cooling fan, in your car. In sealed boat
alternators, the cooling comes from conduction from the core to the case
and it gets lots hotter than your car's alternator, but is designed to do
that. In a large truck alternator on trucks and busses, the alternator
is gear driven directly on the engine block and crankcase oil is poured
through the alternator windings to cool it. They put out hundreds of
amps at 12 or 24 or 32 volts DC.

Now, alternator manufacturers know you are not going to be pulling 70
amps out of a 70 amp alternator for long. (Notice how the current drops,
substantially, after the first 10 minutes of charging caused by the slow
chemical reaction going on in the battery case.) So, the alternators are
not designed to be continuous duty at 70A for days on end like the big
truck alternators are. Economics rears its ugly head. The consumers are
not going to pay for a continuous duty alternator at $500 and the
accountants are not going to let the company produce an alternator that
never fails and makes little profit for the supply chain, so they build
it as cheaply as possible with a little built-in MTBF so you'll buy
another one in a few years. (Notice how many auto electric places are
located in your area.) We could easily build an alternator that would
last a lifetime. Some alternators at power plants are over 80 years old,
having been installed by Mr Tesla, himself. Westinghouse designed them
to run forever. In your alternator, the engineers are depending on
thermal lag to keep the temperature of the alternator below the
temperature it destroys itself, prematurely below the planned
obsolescence target. Simply, we have to keep it below that temperature
until the battery eases the load on it....or else.

Hmm....18V minus 11V for the discharged battery leaves 7V dropped across
the windings. 7V x 70A = 490 watts of waste heat the alternator must
dissipate (damn, I can never remember how to spell that word) through the
case or by the cooling fan. Yep, that case is gonna get HOT! There's
half the power coming out of a bathroom heater made inside there! Now,
as the battery charges, its voltage rises so our 7V alternator drop
drops. The charging current drops rapidly to, say, 20A to complete the
charge in a few minutes, too.
18V-13.5V=4.5V x 20A = 90 watts so the case gets lots cooler after that
initial blast that melted the label off it...(c; Ah, that's better.

Before I get blasted that the voltage regulator makes the alternator
output a flat 14.2V all the time and this is all wrong, look at where
this 14V is measured....at the terminals to the BATTERY. It senses
BATTEYR voltage, not the natural turns ratio voltage of the alternator.
The resistance is BETWEEN the natural voltage of the windings and the
voltage regulator's sensing. The regulator runs it wide open against the
resistance of the windings until the battery voltage trips it. Field
current is reduced to limit battery voltage by making the alternator
weaker. It's natural voltage drops because the magnetic field drops as
the regulator reduces armature field current.

--
There's amazing intelligence in the Universe.
You can tell because none of them ever called Earth.

"Larry" wrote in message
...

Any charging system must have a series resistance to limit charging
current on initial charge. This resistance drops the excess voltage
between the battery's voltage at whatever state of charge it's in, what
the voltmeter in the dash reads, and the charger's natural design
voltage, which is around 18 volts for 12V alternators to make the
charging stable up to 15VDC, giving the regulator something to control.
(Your solar panel chargers run 18V loaded to spec and up to 28V sitting
in the sun totally unloaded. Their internal resistor is the silicon...
(major snippage)

Wow! That was a great post, Larry. Thanks!

Ummm..."MTBF"? Something do do with planned failure from context, but could
you elucidate?

"KLC Lewis" wrote in
et:

Ummm..."MTBF"? Something do do with planned failure from context, but
could you elucidate?





Mean Time Between Failures. It's the tolerance set in the specifications
as to how long it should run, in the mean, between failure modes....

MTBF for the Chinese hard drives in your computer is hundreds of thousands
of hours for $99.

MTBF for a $35,000 American car is one hour past the end of the warranty
period, but they're not really good at making them last that long....

MTBF for a cored boat deck depends on whether it rains or not.

--
There's amazing intelligence in the Universe.
You can tell because none of them ever called Earth.

"Larry" wrote in message
...
"KLC Lewis" wrote in
et:

Ummm..."MTBF"? Something do do with planned failure from context, but
could you elucidate?





Mean Time Between Failures. It's the tolerance set in the specifications
as to how long it should run, in the mean, between failure modes....

MTBF for the Chinese hard drives in your computer is hundreds of thousands
of hours for $99.

MTBF for a $35,000 American car is one hour past the end of the warranty
period, but they're not really good at making them last that long....

MTBF for a cored boat deck depends on whether it rains or not.

--
There's amazing intelligence in the Universe.
You can tell because none of them ever called Earth.

Gotcha! thanks again. :-)

ray lunder wrote in
:

Thanks, Larry. I have a few more questions if you don't mind.
After several hours of digging I found one reference to Marine
Alternator operating temperatures in general and it stated normal
temperatures can run as high as 90 -100C. 90C is 194F so there we are.
It seems this is the upper limit for reliability and I'm probably
going to be without an alternator before long so I need to reduce temp
somehow.

I think you're making a mountain out of nothing. That alternator will be
just fine the way it is. If you don't smell something burning, usually
indicating a shorted rectifier, it's fine! Just run it! We're only
talking less than the boiling point of water, way, way below any damage
point and the temperature isn't going to stay there but just a few
minutes until the battery voltage comes up, when the current drops back.

It's fine!


All good stuff. So is my fan installed correctly? It is sucking air
from the pulley side and pushing it out the back/regulator side. (yes,
it's an internal regulator). The only reference I could find stated
this is incorrect. It should pull from the regulator side and blow out
the pulley end. The fan has a integral spacer around the shaft so it
doesn't look like you can just flip it around.
I asked if the alternator had to rotate in a certain direction and was
told no by the vendor. My engine rotates anti-clockwise as you face
the crankshaft end.
And then,.. The Motorola Marine 70A alternator comes with a 3" pulley.
I swapped it for a 2.5" to speed up the rotation as my crankshaft has
a 4" pulley on a 12hp, one cylinder diesel motor. I figured this would
speed up the alternator, producing more output from a very slow
turning engine and cooling the alt better. (faster fan speed, more air
movement- my reasoning).


Alternators don't have a "wrong direction". They are 3-phase, AC
devices. No matter what, the diodes only rectify in the direction to
make the case negative and the output positive. The fan is also fine.
You can't put it on backwards. Also, you've got the wrong idea about the
speed it rotates. An alternator just above a good idle puts out just as
much current, limited by its build in resistance as one that's just about
to explode from centrifugal force. The other pulley was just fine, too.
GENERATORS put out more current the faster you turn them, not
alternators.

Case in point:
http://www.otherpower.com/
These guys build homebrew wind alternators out of strong magnets and a
disk brake off a car. The turbine only turns it tens of RPM, not
thousands, and it puts out KILOWATTS of power....runs their whole
mountain homes. These are also 3-phase or 6-phase alternators running
into a rectifier bridge to get DC. Amazingly simple machines....turning
very slowly.

You're turning yours so fast it's going to wear the bearings out.
That'll be your premature failure, not the windings. Most alternators
wear down the bearings, then the armature comes into contact with the
stator and that's that....



Which is why some boat owners shop for KKK or "hot rated" alternators
although most vendors have no idea what you're talking about. These
are supposedly built to run at full output for extended periods, like
long enough to charge some deep cycle batteries most of the way up-
say 90 minutes. The alternator doesn't quite cost $500 but the
companion outboard NASA computer 3 step wizbang regulator does. The
budget package starts at $800usd and goes on up to the moon. The
configuration that matches your mounting bracket, footprint, pulley
width/diameter, belt size, output and storage needs will cost much,
much more than the moon. You now need 1/2" or better pulleys, dual
belts, pillow blocks, machine work, sophisticated bank switching and
on and on.

Nonsense....more marketing to the uninformed nonsense. I did a little
Google search as I never heard of your KKK. Here in SC, KKK means
something else...(c;

KKK appears to be a Federal rating system on all systems used in
ambulances:
http://www.nationalvans.com/models/p...cs.pdf#search=
%22KKK%20alternators%22
The specs are tabbed in the panel on the right. In an ambulance, unlike
your boat, we're interested in a high-reliability system that can produce
continuous power to power things, not charge batteries, a totally
different type of load. The ambulance is left RUNNING for hours at a
time at a fast idle, powering the big light show they love so much,
kilowatt sirens to impress the girls, and medical equipment actually
trying to save the patients. This is LOAD power, not charging
power....steady load power. Your application is charging. You're not
going to keep the engine running under a massive load for 8 hours a day.


I couldn't find any reference to which brands/models/manufacturers
where rated and which weren't although there were endless pages of
government bid notices stating the KKK requirement.
Also, 25 - 30% of total capacity is an often published figure for
charge absorption in wet cells, (mine are golf cart style from Dyno in
Ballard) which works out to 60 odd amps in this case so in theory from
a 50% discharge I should be able to charge at nearly full rate for 2
hours and be up again. It would seem the difference between theory and
practice is different than it is in theory. So why does the amp output
go down after 10 minutes? Does the regulator sense it's getting too
hot and reduce the field voltage?
Also, how does an internal regulator operate after the battery voltage
is up to say 12.65V, which is fully charged in my case. There seems
to be a lag, both charging and discharging, between the voltage being
up and the current capacity being at it's fullest.
Also, having no direct access to the field winding with an internally
regulated unit, is there a way to disable the alternator and get back
the horsepower, like to buck a tide or something?

Heavily charging for 2 hours will put a nice SURFACE charge on your
battery bank. This is always a dream on the newsgroup every 3 weeks.
Unfortunately, we're talking about the same lead acid batteries that are
over 100 years old. There is no "supercharging" a lead acid battery.
The chemical reaction of recharging a lead acid battery is a SLOW
process. What happens with heavy currents is that in between the plates,
the lead sulphate ions that are lucky enough to be there are quickly
turned back into lead, plating the plates. That's great....er, ah,
except we're going to run out of lead sulphate ions, quickly, faster than
the electrolyte can circulate more of them from outside the separators.
So, you keep shoving the current up and up. What happens between the
plates is that all this current with no lead sulphate ions to speak of in
between leaves Sulphuric Acid diluted in distilled water. Sulphuric acid
is unimpressed. The water it's diluted in, however, is easily broken
down into its component parts. The battery becomes a great hydrogen
generator! The hydrogen combines into H2 gas and the battery starts
bubbling like mad as long as you leave all this current on. The battery
"gasses", as its water is used up, leaving CONCENTRATED SULPHURIC ACID in
its wake to destroy the lower part of the plates, the part still
submerged in it. The water being consumed lowers the electrolyte as it's
consumed and from the cap holes, the battery looks "empty", even dry up
on top. You destroyed it trying to charge it in 15 minutes with your
huge alternator and super regulator.

To avoid this stupidity, the regulator is set to back off on the field
magnetism when the battery voltage reaches 14.2 volts, its normal
charging voltage. Lead acid batteries use float chargers, chargers that
measure voltage, not current. The current regulates itself to a safe,
SLOW CHARGING level that gives the electrolyte time to circulate more
lead sulphate ions in between the plates, no easy task, so you can
continue to plate the plates with new lead, replacing what the acid ate
while discharging. You, a typical boater, get all depressed as the 8
ammeters distributed throughout the boat drop off to 20 amps quite
quickly, as quickly as the electrolyte runs out of ions which causes the
battery's voltage to rise as its internal resistance to the charging
current in this condition does, causing the regulator to sense the rise
and turn down the current even more. It's all quite natural. Nothing is
wrong with anything. Charging is a SLOW process, the slower, the better!

Want to test what I say? That's easy. Discharge the house batteries a
ways. Start the engine and run it up until the ammeter is as high as it
will go. (More speed won't help past that point, just wastes fuel.) As
soon as the current starts dropping back from the lack of ions between
the plates, cut the engine. Wait 30 minutes...(This is the hard parts
for Americans used to having everything instantaneously.) Crank the
engine again and notice you're back at 70A! The ions were replaced in
the electrolyte soup you used up the first time. But, alas, you notice
the ammeter drops back in LESS time, now, because the total available
ions is more dilute and charged back faster. If you repeat the cycle, it
happens faster each time. (Don't forget you're using up the starting
battery playing this game with me, so leave the engine running to
recharge it after the game is over.)

Buying a 500 amp alternator will not change physics and chemistry. The
500A alternator with a PROPER REGULATOR will drop back to the SAME
current level at the SAME time as soon as the battery voltage reaches a
charging voltage of 14.2V and the huge regulator on the beast drops back
the current to 20A like the battery has, by its voltage, requested. It
takes just about as long to charge on a 500A alternator as it does on a
50A alternator. The difference only being the initial blast of current
from the 500A alternator warps the plates by overheating them with way-
too-much internal current, maybe destroying them.

How much is too much? 25% of the total amp-hour rating of the house
batteries. Two 6V golf cart batteries in series = 230 AH unless you've
laid out big bucks. 25% of 230AH = 57.5A A 60 amp alternator will be
just fine. Mine is...(c; Initial charging of 60A isn't dangerous to
warping the plates and the current drops back just fine as the battery
voltage comes up from the SIMPLE, INEXPENSIVE internal regulator
monitoring the voltage at the output terminal. The system is perfect....

Got two banks of golf cart batteries in parallel? Get the 120A
alternator to charge them simultaneously, just like the one on Lionheart,
my buddy's Amel Sharki ketch's old, faithful Perkins 4-108 tractor motor.

Crank the diesel, idle it at 1000 RPM, sit back and RELAX! The batteries
and regulator will take care of things for you just fine, without wasting
a few thouand dollars on electronic gadgets and step charging and all
that marketing BULL****! That little diesel of yours will IDLE at that
speed a month on 10 gallons of fuel in neutral. Every hour or so, put it
in gear and run it wide open for 5 minutes to keep it from coking up, a
problem with diesels. It's fine....



That makes the armature R a tenth of an ohm at full output?

Yeah, something like that. You'd have to make a 4-terminal resistance
test to measure it. It isn't much. Doesn't need to be. It's just
enough to limit the current to a safe level to protect the diodes and
windings.




Just for grins, how do you calculate watts to degrees?
My battery went from 11.75V to 12.3 in 1/2hour of running. That's when
I noticed it was so hot. I didn't get an amp reading that time.

Too many variables for simple arithmeticians like me. You'd need to
calculate or measure the curve of heat dissipation (god I hate that word
as I can never remember how to spell it) the alternator is capable of
but, you'd have to use calculus from all the variables like airflow in
the engine compartment, compartment temperature, humidity, conduction to
the block (in both directions because the block gets hotter than the
air), etc. The alternator temperature is a huge combination of heat
produced minus all the paths to pull heat away from the core....very
complex mathematics, indeed.

Your battery voltage rising was because of my explanation in the
paragraphs above....(c; The voltage regulator was still running the
alternator at maximum folding current at 12.3V. It probably had pulled
the current back some (it's quite linear as it's cheap), but not much,
hence the hot alternator. Internal regulators like your also have
temperature sensors in them the fancy external regulator boys don't get.
A simple thermister in the device is part of its analog programming. The
regulator's mounted on the case so it can feel the case temperature.
Neat, huh?


So back to the internal regulator. I'm still confused. On one hand it
looks like the regulator scales the amperage output; full output
initially, roughly half and then switching on and off as the full
battery voltage rides fractionally up and down over a set point of say
14V. Which looks like a multi stage charger to me.
On the other hand it looks like it puts out a flat maximum output or
nothing and measurements are skewed by an obscure interaction between
the changing resistance of the alternator windings due to their
temperature and the changing internal resistance of the battery as it
accepts a charge and sees it equalized between the plate surface and
the interior of the plate for each cell and between the cells
themselves.
Expatiate?


Nope, too many computers, no analog experience. On and off are for
computers. As the battery voltage rises, the ANALOG regulator simply
scales back on the rotor current that makes the rotating magnetic field
for the stator to use. Less field, less power, less current. It's
programming is real complex....a couple of resistors...(c; It runs the
field current along an analog curve the engineers who designed it decided
on...all quite simple. Alternators like my old '73 Mercedes Benz Diesel
has with MECHANICAL regulators buzzing away DO pulse the rotor current!
The mechanical regulator stays full on, limiting the rotor current with a
really hot little wire-wound resistor to a safe level, until the voltage
sense relay, the little relay of the three inside it that has a gazillion
turns of wire because it's right across the battery posts. When that
relay starts pulling in, releasing because it pulled in and turned off
the field current, dropping out to charge again, pulling in again because
the battery voltage came back up....a thousand times a minute. What we
get is an AVERAGE charging current from these rapid pulses of on and off.
If you listen to the case of the old mechanical regulator, you can hear
it buzzing on and off...average rotor current keeps dropping because the
regulator stays off more and more than it clicks on, until the battery is
charged, when it rarely clicks on again because the battery voltage is
enough to keep the voltage sense relay pulled in....well, until you turn
on the headlights and heater fan. The regulator, a Bosch, in the '73 is
33 years old. It's solid state, you know....no tubes!....(c;

Now, let's forget all this charger nonsense and figure out which wine
will go with that steak we're going to put on the grill tonight....the
real important boat stuff!