Can an alternator be to big?

[Glenn Ashmore]

I have been offered a really good deal on a high amp (325 amp) fire engine
alternator by the city vehicle maintenance shop. It was purchased as a test
unit but due to some budget cutbacks ended up being to expensive to equip
the whole fleet. This monster is hot rated at 200 amps at 2,000 rpm and
275 amps at 4000 rpm. I am thinking about buying it and keeping the 200 amp
Leece Neville as a spare.

My battery bank is 850AH of L16HC wet cells that can take 200 amps in bulk
charge. Is my Xantrex smart regulator going to keep this monster from
cooking my battery bank?

--
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]

Don't think there will be a problem there. The alternator mount is already
set up for dual BX cogged belts which should be able to handle 12HP. I did
that because I didn't want that Leese Neville squealing. Because this thing
puts out a lot more amps at lower RPM than the LN I think I will increase
the pulley diameter which should increase the power handling capacity even
more.

--
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

 

[Larry]

And belts and slippage
may also limit charging current.

May?
..
..
..
..
..
WILL!

325A x 14V = 4550 watts divided by 746W/hp = 6.1 HP plus the conversion
losses, probably over 10HP.

How big was that Yanmar 2GM in that boat??....(c;

How many HP is a V-belt capable of delivering at 2000 RPM, anyways?

How many pulley Vs does the alternator's pulley have, if it has pulleys at
all?

Two fan belts are NOT going to pull a 200 or 325A alternator for long.....
It's hard enough to keep a 120A fan belt from squealing....

 

[Glenn Ashmore]

Actually reducing the alternator RPM is the idea. This thing puts out
200Amps at an alternator speed under 2000 RPM. With the pulleys I have now
that is an engine speed of about 800 RPM. I need to get the engine turning
faster or the power will be all torque and no speed and Larry's prediction
of gloom and doom might come true. A pair of BX belts can handle plenty of
HP but not at such low speeds.

After some research I found some interesting things about this monster.
There are actually two rotors on the same shaft. One is high power
permanent magnets and the other is a regular Lundell claw & field coil.
With the field coil off the magnets will drive the alternator to 200 amps at
4,000 RPM. If more power is needed to maintain voltage the field coil is
energized to add to the flux and produce up to 305 amps. If less power is
needed the coil is reversed to cancel out the flux field. Net result is a
70% increase in efficiency and a corresponding reduction in heat build up
but to get minimum output the field coil has to be driven at full power
backwards.

The down side is you can't use a 3 stage regulator. This puppy is designed
to crank out power for lights, inverters and equipment. Control is strictly
on the output voltage so it stays in bulk stage until the batteries can't
take any more. This is going to take some more thought. For the price
though it would be a good temporary high output spare.

--
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

 

[Paul Hovnanian P.E.]

Actually reducing the alternator RPM is the idea. This thing puts out
200Amps at an alternator speed under 2000 RPM. With the pulleys I have now
that is an engine speed of about 800 RPM. I need to get the engine turning
faster or the power will be all torque and no speed and Larry's prediction
of gloom and doom might come true. A pair of BX belts can handle plenty of
HP but not at such low speeds.

Actually, the alternator will put out whatever the battery and loads
require. Unless you are charging a huge battery bank and/or have 200 A
load connected to it, it won't put out that much. Given the electrical
(and mechanical) losses, the input HP will be whatever are needed to
provide the electrical output. The larger alternator will have lower
electrical losses, but higher mechanical. All in all, this unit won't
present a mechanical load significantly different than a smaller
alternator.

After some research I found some interesting things about this monster.
There are actually two rotors on the same shaft. One is high power
permanent magnets and the other is a regular Lundell claw & field coil.
With the field coil off the magnets will drive the alternator to 200 amps at
4,000 RPM. If more power is needed to maintain voltage the field coil is
energized to add to the flux and produce up to 305 amps. If less power is
needed the coil is reversed to cancel out the flux field. Net result is a
70% increase in efficiency and a corresponding reduction in heat build up
but to get minimum output the field coil has to be driven at full power
backwards.

This unit must be matched to the appropriate regulator. If you didn't
get one with the alternator, the deal may not have been that good.

 

[Glenn Ashmore]

Actually, the alternator will put out whatever the battery and loads
require. Unless you are charging a huge battery bank and/or have 200 A
load connected to it, it won't put out that much. Given the electrical
(and mechanical) losses, the input HP will be whatever are needed to
provide the electrical output. The larger alternator will have lower
electrical losses, but higher mechanical. All in all, this unit won't
present a mechanical load significantly different than a smaller
alternator.

That's just it. There will definitely be a heavy load on it. When it
cranks up every morning it will be seeing a 900AH battery bank ready to take
the first 225 amps in bulk mode.

This unit must be matched to the appropriate regulator. If you didn't
get one with the alternator, the deal may not have been that good.

It has the regulator built in. Pretty interesting one too. Even has a
battery voltage sense connection. However the regulator does not have a way
to change from bulk to absorption to float modes and there is no
equalization. The shore power charger can handle the equalization and with
my normal use pattern of 50% to 85% charge will rarely need float except at
the dock but it would be nice to have optomized bulk and absorption ability.

--
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]

Everything you attach to the engine reduces the HP output. How much,
good question. But having an alternator that is far bigger than your
needs is a waste. Additionally, to make use of that power you need to
get it to the battery banks. If the wire between the alternator and
battery is too small to handle the current, or the wire between the
battery and load center (electrical pannel) is too small, it could burn
up under a heavy load if it's not fused properly. Your probably going
to end up cooking something, lets hope it's not the boat while your on
it. Also, if it's not CG approved, and you have a fire because of it,
your insurance company is going to walk away, it's your problem. I'd
stick with the normal marine alternator if I was you.

No real problem there. Because if the higher efficiency the HP charts say
it will take less power than the 200A Leese Neville that is in there now. I
have 4/0 to the 850AH bank and the inverter and 2/0 to the breaker panel.
At idle speed it will theoretically put out up to 240 amps which will cover
the 225A the battery bank needs in bulk mode with a little left over for
house loads.

The alternator is an Eco Tech 305. Apparently they are becoming popular
with the commercial fishing boats in the NW. The regulator is set for 14.4
volts so while it may take a little longer in bulk mode it will be just
right for absorption. I just need to figure a way to turn it off when
motoring through a couple of days of no wind. Not a good idea to hold a
fully charged battery at 14.4V for very long.

Go2Marine has them on their site listed at $2K. The city is asking $375. I
think I am going to take them up on it.


--
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

 

[Larry]

Also, if it's not CG approved, and you have a fire because of it,
your insurance company is going to walk away, it's your problem. I'd
stick with the normal marine alternator if I was you.

I think THAT is a very important point, too....

 

[GBM]

There used to be a manual alternator regulator called an Automac, sold by
Weems & Plath - This allowed the alternator output to be manually adjusted.
These are no longer sold, but perhaps someone else sells something like
that? Or perhaps drive it through a clutch that can be disengaged and keep
a smaller alternator in service?

I can understand that the price is attractive, but I would be careful with
that beast! Unless of course, if you plan on doing some welding Usually
better to have multiple smaller units. Ventilation and cooling may need to
be addressed - will you get enough cooling in your engine room as compared
with the intended installation for those units?

BUT, if you have the HP to drive it, it does sound like an interesting
unit - especially the low speed output.

GBM

 

[Glenn Ashmore]

This thing uses a J-180 mount same as the Leece Neville so it will basically
be a drop in. Also supposed to generate less heat so the duct work I
installed for the LN should be more than adequate.

The weird thing about this alternator is that the primary magnetic field is
from the permanent magnets on the rotor so as long as it is turning it is
generating power. The way you turn it off is to run the field current in
reverse to cancel out the magnets. That greatly increase the efficiency but
means it can't use a normal external regulator.

--
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]

The surveyor that my insurance company hired to monitor my progress has seen
the Leese Neville which is not "USCG approved" and accepted it with out
reservation.

Actually neither 46 CFR 176 or 46 CFR 183 require approval of alternators in
diesel powered environments. The only source I can find that recommends
using only marine approved alternators is our friend David Pasco and he even
has the reference to the requirements wrong. J1527 is specific to hose
standards, not alternators.

--
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

 

[Peter Albright]

Glen,

Have you considered biasing the voltage sense line, to adjust the regulator
output voltage?

Peter Albright,
Tampa, FL

 

[Glenn Ashmore]

Glen,

Have you considered biasing the voltage sense line, to adjust the
regulator output voltage?

I have been thinking about that. Looks like that would be the only way to
control it. The internal regulator is set to maintain 14.4V on the sense
line. Boosting the sense line 1.2V would bring the output down to a safe
13.2V float. You could actually put a microprocessor to sense the battery
voltage and bias the alternator sense to do everything a "smart" regulator
does but that would be more work than I have time for.

--
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

 

[Paul Hovnanian P.E.]

That's just it. There will definitely be a heavy load on it. When it
cranks up every morning it will be seeing a 900AH battery bank ready to take
the first 225 amps in bulk mode.


It has the regulator built in. Pretty interesting one too. Even has a
battery voltage sense connection. However the regulator does not have a way
to change from bulk to absorption to float modes and there is no
equalization. The shore power charger can handle the equalization and with
my normal use pattern of 50% to 85% charge will rarely need float except at
the dock but it would be nice to have optomized bulk and absorption ability.

That could be a problem. If you could tweak the voltage setting down a
bit, you could slow down the battery charge rate and the resulting
engine load.

Petes's suggestion is pretty good. Put in some current sensing on the
gen. output and use that to bump the V sense line up as the generator
output approaches a setting suitable to your prime mover. You'll need a
gain control to set the V bias per amp load and set it so that the
system remains stable.