hello all
is it possible to link 2 or more car alternators driven from the same engine
to a single battery
thankyou David

No, not at the same time. Use a selector switch and a relay.
Steve
"david scheer" wrote in message
u...
hello all
is it possible to link 2 or more car alternators driven from the same
engine
to a single battery
thankyou David

hello all
is it possible to link 2 or more car alternators driven from the same engine
to a single battery
thankyou David


Yes, it works fine, no special hookup needed other than trying to get the
voltage regulator settings as closely matched as possible if you want both alts
to contribute their fair share of charging current. Many fishing boats use this
even without a perfect voltage match so that if one alt fails, the other is
online and you can keep fishing.

(BOEING377) wrote in
:

hello all
is it possible to link 2 or more car alternators driven from the same
engine to a single battery
thankyou David


Yes, it works fine, no special hookup needed other than trying to get
the voltage regulator settings as closely matched as possible if you
want both alts to contribute their fair share of charging current.
Many fishing boats use this even without a perfect voltage match so
that if one alt fails, the other is online and you can keep fishing.


Lionheart has two alternators on her Perkins 4-108 diesel. If I put our
engine battery switch in "Both", the effect is that the 80A starting
battery alternator is parallelled with the 170A house battery alternator.
No special tweaking of fixed regulators was done.

If some of the batteries are low, such as discharged house batteries, both
alternators pull like hell at god-awful currents until the voltage on the
two 700AH house battery banks comes up. Then, having the lowest voltage
set regulator, the 80A simply shuts down when its voltage regulator set is
reached, while the 170A pulls whatever it pulls as the battery voltage
comes up.

It's an old wives tale you can't connect them in parallel. As someone else
posted, commercial boats do it all the time.....but, of course, they don't
have that expert help from the boater working at West Marine or the Yacht
Club Bar....(c; All yachties need to ride, underway, in the engine room of
a shrimp boat or commercial fishing vessel. It would give them all a touch
of reality....

Larry

Do so at your own risk. Yes it will work as long as all components are
functional. If there is a fault, it will damage both systems. Ask yourself
why anyone would wish to combine alternators on the same battery bank at the
same time. It is self defeating. Each alternator should have the ability to
charge any of the battery banks and any battery bank should be able to power
any load and all options will be covered without risk.
Steve
"Larry W4CSC" wrote in message
...
(BOEING377) wrote in
:

hello all
is it possible to link 2 or more car alternators driven from the same
engine to a single battery
thankyou David


Yes, it works fine, no special hookup needed other than trying to get
the voltage regulator settings as closely matched as possible if you
want both alts to contribute their fair share of charging current.
Many fishing boats use this even without a perfect voltage match so
that if one alt fails, the other is online and you can keep fishing.


Lionheart has two alternators on her Perkins 4-108 diesel. If I put our
engine battery switch in "Both", the effect is that the 80A starting
battery alternator is parallelled with the 170A house battery alternator.
No special tweaking of fixed regulators was done.

If some of the batteries are low, such as discharged house batteries, both
alternators pull like hell at god-awful currents until the voltage on the
two 700AH house battery banks comes up. Then, having the lowest voltage
set regulator, the 80A simply shuts down when its voltage regulator set is
reached, while the 170A pulls whatever it pulls as the battery voltage
comes up.

It's an old wives tale you can't connect them in parallel. As someone
else
posted, commercial boats do it all the time.....but, of course, they don't
have that expert help from the boater working at West Marine or the Yacht
Club Bar....(c; All yachties need to ride, underway, in the engine room
of
a shrimp boat or commercial fishing vessel. It would give them all a
touch
of reality....

Larry

"Steve Lusardi" wrote in message
...
Do so at your own risk. Yes it will work as long as all components are
functional. If there is a fault, it will damage both systems.

There is no extra risk. Each alternator has a diode bridge at its output, so
current cannot flow from one alternator to the other. If such a bridge
fails, it either isolates completely (no harm done) or is lets current flow
from the terminals through the windings. In this case, the result will be
the same on a single alternator with the same failu it will burn out.

Meindert

Do so at your own risk. Yes it will work as long as all components are
functional. If there is a fault, it will damage both systems. Ask yourself
why anyone would wish to combine alternators on the same battery bank at the
same time. It is self defeating.

Not really. It provides unattended backup charging if one alternator fails.
Although it certainly is theoretically possible that a failure could damage
something, I have yet to see it happen in a dual alt charging system on
commercial fishing boats which often put thousands of hours per year on their
gear. Get two Niefhoff or Electrodyne industrial strength brushless alternators
with integral regulators and your alternator troubles are over. You just won't
think about alternators anymore instead of fretting about multistage charging,
brush wear, bearing wear, AC output from diode failure, etc. These beasts just
do one thing and they do it exceedingly well: put out a fixed voltage DC no
matter what. They (both brands) seem to last forever, long after the other
alternators (Moto, Leece, Delco, Balmar etc) are needing overhauls these guys
just keep ticking. Well, you might fret about their initial cost, but believe
me they are worth it. You'll also get less RF noise with the brushless alts, a
plus for HF radio users.

I use 3 alternators on 1 system, have had no trouble.
2 80A units are on my auxiliary engine, and are controlled by 1 regulator.
the other is on the propulsion engine and has it's own regulator. [
http://www.amsterdamhouseboats.com/v..._regulator.htm ]
I've found that with separate regulators, 1 unit will do all the work until
it starts getting hot, then it's protection circuitry starts tapering the
output and the second alternator takes some load. this leads to unnecessary
belt wear on the first alternator, as well as inefficiency. when they share
1 regulator, output, belt load, and heat are evenly split [I measured the
outputs].
if 1 huge machine fits your engine and your budget, go for it; but 2
separate units working together run fine, too.
regards, Mark Holden

"Steve Lusardi" wrote in message
...
Do so at your own risk. Yes it will work as long as all components are
functional. If there is a fault, it will damage both systems. Ask yourself
why anyone would wish to combine alternators on the same battery bank at
the
same time. It is self defeating. Each alternator should have the ability
to
charge any of the battery banks and any battery bank should be able to
power
any load and all options will be covered without risk.
Steve
"Larry W4CSC" wrote in message
...
(BOEING377) wrote in
:

hello all
is it possible to link 2 or more car alternators driven from the same
engine to a single battery
thankyou David


Yes, it works fine, no special hookup needed other than trying to get
the voltage regulator settings as closely matched as possible if you
want both alts to contribute their fair share of charging current.
Many fishing boats use this even without a perfect voltage match so
that if one alt fails, the other is online and you can keep fishing.


Lionheart has two alternators on her Perkins 4-108 diesel. If I put our
engine battery switch in "Both", the effect is that the 80A starting
battery alternator is parallelled with the 170A house battery
alternator.
No special tweaking of fixed regulators was done.

If some of the batteries are low, such as discharged house batteries,
both
alternators pull like hell at god-awful currents until the voltage on
the
two 700AH house battery banks comes up. Then, having the lowest voltage
set regulator, the 80A simply shuts down when its voltage regulator set
is
reached, while the 170A pulls whatever it pulls as the battery voltage
comes up.

It's an old wives tale you can't connect them in parallel. As someone
else
posted, commercial boats do it all the time.....but, of course, they
don't
have that expert help from the boater working at West Marine or the
Yacht
Club Bar....(c; All yachties need to ride, underway, in the engine room
of
a shrimp boat or commercial fishing vessel. It would give them all a
touch
of reality....

Larry

(BOEING377) wrote in
:

etc) are needing overhauls these guys just keep ticking. Well, you
might fret about their initial cost, but believe me they are worth it.
You'll also get less RF noise with the brushless alts, a plus for HF
radio users.


Very well said. Thank you. I don't know where these "dock wives tales",
like hooking alternators in parallel comes from, but it's just not true.

Whether a diode shorts in one alternator, whether parallel connected or
not, the shorted diode simply melts open! The 3 phase diode bridge is
permanently connected across the monster batteries, whether the alternator
is "on" or not. Any diode that shorts is simply, internally, melted apart
by the ensuing current surge, leaving the 3-phase bridge now a 1-phase
bridge because they are connected in delta. The "bad alternator" now puts
out much less current on one phase than it did before. You'll hear it
whenever they transmit a radio as "alternator whine" at a much lower pitch
than when they have a good alternator, but a dead cell in the battery. The
remaining connection pulses the battery wide open trying to satisfy the
regulator. It never makes it.

Because the shorted diode only lasts milliseconds, before the battery's
current melts it, the other alternator is in no danger, whatsoever, and it
will simply take up the loads, if it can. The only drawback to this is
you'll not know the first alternator failed until the second alternator
failed, so it would be a good idea to put a separate ammeter shunt in each
alternator's output so you can see which alternator is pulling what load,
not just one shunt between them.

Even operating normally, one alternator's regulator will shut down first,
the one with the lowest regulator setting. No two regulators are ever
going to hold the same exact float voltage. This is fine because when the
system reaches this float voltage, you won't need both alternator,
anyways....

Larry