"CS" wrote in news:1160512470.107776.32410
@c28g2000cwb.googlegroups.com:

I've got 2 options - the easy one - disconnect the wire - is an
overspeed really necessary or useful??
Try and get a device to divide the frequency.



As alternator speed has NOTHING to do with its output once it's just off
idle, why not put the right pulley back on it, correcting the problem and
saving the alternator bearings from overspeed, themselves...premature
failure.

Spinning an alternator so fast DOESN'T make it put out another amp....

No, you can't charge the house batteries in 5 minutes, either....(sigh)


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

As alternator speed has NOTHING to do with its output once it's just off
idle, why not put the right pulley back on it, correcting the problem and
saving the alternator bearings from overspeed, themselves...premature
failure.
Spinning an alternator so fast DOESN'T make it put out another amp....

COMPLETELY INCORRECT - look at the output curve for the alternator here
-
http://www.prestolite.com/images_alt...161U_curve.pdf

At engine idle, alt will be at 2500 and deliver 85A. With old pulley
off original alt, alt is only at 1500rpm and output is only 35A - so
quite a useful increase.

Output therefore CLEARLY varies considerably with speed and the spec
sheet I got from Prestolite has it continuously rated for 8000 rpm - so
it is not being overspeeded.

Fundamental AC - the higher the freq (= more rpm) the greater the power
that can be transmitted. Which is why aircraft AC systems are often at
400Hz - smaller kit but higher power.

No, you can't charge the house batteries in 5 minutes, either....(sigh)

At 110A a 920Ah battery is going to charge a hell of a lot quicker than
at 50A. I'll leave you to do the sums.

Higher AC frequencies are good for transformers, but don't have an effect on the
transmission of power reasonable distances and a boat is way smaller than that.
But since your AC is being converted to DC, the transformer argument is
irrelevant.

And your AC frequency will be pretty high start with -- there's more than one
cycle per rev.

"CS" wrote in message ups.com...
As alternator speed has NOTHING to do with its output once it's just off
idle, why not put the right pulley back on it, correcting the problem and
saving the alternator bearings from overspeed, themselves...premature
failure.
Spinning an alternator so fast DOESN'T make it put out another amp....

COMPLETELY INCORRECT - look at the output curve for the alternator here
-
http://www.prestolite.com/images_alt...161U_curve.pdf

At engine idle, alt will be at 2500 and deliver 85A. With old pulley
off original alt, alt is only at 1500rpm and output is only 35A - so
quite a useful increase.

Output therefore CLEARLY varies considerably with speed and the spec
sheet I got from Prestolite has it continuously rated for 8000 rpm - so
it is not being overspeeded.

Fundamental AC - the higher the freq (= more rpm) the greater the power
that can be transmitted. Which is why aircraft AC systems are often at
400Hz - smaller kit but higher power.

No, you can't charge the house batteries in 5 minutes, either....(sigh)

At 110A a 920Ah battery is going to charge a hell of a lot quicker than
at 50A. I'll leave you to do the sums.

Higher AC frequencies are good for transformers, but don't have an effect on the
transmission of power reasonable distances and a boat is way smaller than that.
But since your AC is being converted to DC, the transformer argument is
irrelevant.

I'm lost - I have not mentioned transformers???

And your AC frequency will be pretty high start with -- there's more than one
cycle per rev.

Yes, a 10 pole alt at 8000 rpm is generating AC at around 1332Hz. More
A can be produced at 1332Hz than at 50Hz.

Fundamental AC - the higher the freq (= more rpm) the greater the power
that can be transmitted. Which is why aircraft AC systems are often at
400Hz - smaller kit but higher power.

I was explaining why aircraft sometimes use 400Hz AC -- because they can carry
smaller transformers.

I won't disagree that you can generate (not transmit) more power by spinning the
alternator faster (up to a limit).

"CS" wrote in message ups.com...


Higher AC frequencies are good for transformers, but don't have an effect on the
transmission of power reasonable distances and a boat is way smaller than that.
But since your AC is being converted to DC, the transformer argument is
irrelevant.

I'm lost - I have not mentioned transformers???

And your AC frequency will be pretty high start with -- there's more than one
cycle per rev.

Yes, a 10 pole alt at 8000 rpm is generating AC at around 1332Hz. More
A can be produced at 1332Hz than at 50Hz.

"CS" wrote in news:1160536091.872456.50110
@m73g2000cwd.googlegroups.com:

At 110A a 920Ah battery is going to charge a hell of a lot quicker than
at 50A. I'll leave you to do the sums.




Hmm.....is the regulator shorted?....

Over and over boaters report on here how quickly their huge battery banks
drop off full current to 20A or 30A, tapering quickly to their
consternation as the regulators do their jobs, much to their dismay....

LEAD ACID BATTERIES CHARGE VERY SLOWLY....hours and hours.

You CANNOT charge a 920AH battery from 50% to full charge in the 5
minutes they all want to run the engine charging
batteries................yet.

However, the solution IS on the radar:
http://www.toshiba.co.jp/about/press/2005_03/pr2901.htm
80% in 60 seconds....
100% in 3 minutes flat....
99% charge recovery after 1000 deep, deep cycles!

Hmmm...the sums....950 AH new Li-Ion nanobeast charge in 60 seconds to
80% = 760AH....that would be 760A if we charged it in an hour but we're
gonna charge it 60 times faster than that so 760A x 60 = 45,600A X 14.2V
= 647,520 watts for 60 seconds divided by 746w/HP = 867HP for a
minute....Hmm....don't think the Yanmar 3GM is gonna like that....How
many v-belts does it take to drive a 45,600A alternator, anyways?? Can
we mount the 700KW alternator where the aft cabin used to be?

Maybe it'll charge it on your 110A charger running wide open for 950
divided by 110 = 8.6 hours....does that sound better? The new battery
won't even get warm at 110 amps...It's internal resistance must be in
nano-ohms to take a huge charging current like they do.

Thankfully, the 1920's technology lead-acid wetcell's days are
numbered.... Still no news I've found when the Nano-Li-Ions will be
marketed. I suspect the auto and oil industries are heavily pressuring
Toshiba and the other developers to flush the damned inventor and his
notes down the toilet like they did all the EV cars (EV-1/GM remember
them? All EV-1s were confiscated and crushed after dealers bitched they
wouldn't need constant, expensive maintenance and repairs, the dealer's
gravy train.) With THIS battery, the EV-1 would refuel in less time than
it took to refill the Ford Exploder at god-awful amps/volts and every
time you pressed the "brake" pedal, the huge power generated would
restore the charge on the new Li-Ion cells under the trunk, instantly,
not wasted trying to charge slowcharge batteries like now. Man, what an
electric car we'd have if the *******s in control don't bury it, again!

A side note: I've seen the webpage of the Dell notebook with the
defective Li-Ion battery exploding on some conference table in a hotel.
Very violent and very hot! It was about 4AH...Wonder what the fire will
look like on a 950A Li-Ion house battery?? Will there be any boat left?
There wasn't much notebook left...or table it was sitting on!

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

"Larry" wrote

As alternator speed has NOTHING to do with its output once it's just off
idle, why not put the right pulley back on it, correcting the problem and
saving the alternator bearings from overspeed, themselves...premature
failure.

Spinning an alternator so fast DOESN'T make it put out another amp....

Look at any alternator output curve and you will see that amps increase as
RPM increases up to the point where they approach full output and then level
out. That point is usually between 2500 and 3500 shaft RPM. There are a
very few very expensive alternators, like the Eco-Tech, that are built to
produce close to full output at less than 2000 RPM that have a very steep
curve but most alternators require a minimum 2500 RPM to reach any
significant output.

That said, the OP's choice of alternators may not be the best if he wants to
charge at dead idle. The output curve has a particularly slow slope. He
should also consider that it takes a certain amount of power to produce 85
amps. Besides the output, the other item on that chart he should consider
is the Torque curve. When you use a pulley ratio that allows close to full
output at 800 engine RPM the torque increases to the point that invites belt
failure and excessive side loads on bearings.

His best option is to reduce the ratio closer to the original and charge at
1200 to 1500 engine RPM.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

Look at any alternator output curve and you will see that amps increase as
RPM increases up to the point where they approach full output and then level
out. That point is usually between 2500 and 3500 shaft RPM. There are a
very few very expensive alternators, like the Eco-Tech, that are built to
produce close to full output at less than 2000 RPM that have a very steep
curve but most alternators require a minimum 2500 RPM to reach any
significant output.

Look at the LN curve I've posted - it is not as stated above. Full
output is at 5000 alt rpm and it then levels out.

That said, the OP's choice of alternators may not be the best if he wants to
charge at dead idle. The output curve has a particularly slow slope. He
should also consider that it takes a certain amount of power to produce 85
amps. Besides the output, the other item on that chart he should consider
is the Torque curve. When you use a pulley ratio that allows close to full
output at 800 engine RPM the torque increases to the point that invites belt
failure and excessive side loads on bearings.

My engine can deliver up to 20kW at engine idle according to the makers
engine manual - more than enough for the 2 - 3 kW taken by the
alternator. Torque will also not be an issue with dual belts.

Look at the LN curve I've posted - it is not as stated above. Full
output is at 5000 alt rpm and it then levels out.

That is what I meant about "OP's choice of alternators may not be the best
". That particular alternator has a relatively slow slope up to full power.

My engine can deliver up to 20kW at engine idle according to the makers
engine manual - more than enough for the 2 - 3 kW taken by the
alternator. Torque will also not be an issue with dual belts.

Off which end? My Yanmar can handle a lot of torque off the back end but
the front crankshaft bearings are not designed to handle a lot of side load.
Double belts will stop the slippage but a double pulley extends the center
of load further from the bearing increasing the leverage of the side load.

There is also the principle that diesel engines are much happier running at
1800 RPM than they are at 800. For many reasons running at idle under light
loads for long periods is hard on diesels. I am not saying don't do it.
Just that there are better ways to tackle the problem.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

Glenn Ashmore wrote:

Look at the LN curve I've posted - it is not as stated above. Full
output is at 5000 alt rpm and it then levels out.

That is what I meant about "OP's choice of alternators may not be the best
". That particular alternator has a relatively slow slope up to full power.

My engine can deliver up to 20kW at engine idle according to the makers
engine manual - more than enough for the 2 - 3 kW taken by the
alternator. Torque will also not be an issue with dual belts.

Off which end? My Yanmar can handle a lot of torque off the back end but
the front crankshaft bearings are not designed to handle a lot of side load.
Double belts will stop the slippage but a double pulley extends the center
of load further from the bearing increasing the leverage of the side load.

Off the front crankshaft and or a PTO shaft. The engine is an 8 litre
6 cyl natural aspirated 160 Hp engine which weights 1000kg and is a
proper industrial marine engine as used by fishing vessels - not a
bleeding micky mouse Yanmar engine designed for pleasure yachts. I
have done a certain amount of research and I am amazed by the complete
rubbish being spouted about alternators.