electrical question - 2 generators/alternators
 

I have a question that I would appreciate an answer to from anyone who has a
clue.

My question is this: can you have 2 generators (or alternators) charging
the same battery bank at the same time? For example, if I have 2 wind
generators will they both charge my house bank simultaneously? Or, can only
one generator/alternator be in use at one time?

Thanks in advance.
Mark

electrical question - 2 generators/alternators
 

Mark Newcomb wrote:
I have a question that I would appreciate an answer to from anyone who has a
clue.

My question is this: can you have 2 generators (or alternators) charging
the same battery bank at the same time? For example, if I have 2 wind
generators will they both charge my house bank simultaneously? Or, can only
one generator/alternator be in use at one time?

IMO: Could cause problems. It would be safer if you put at least one
blocking diode or rectifier in the circuit. Maybe a selenium rectifiers
that is rated at current qs to handle the generators output like those
used in motorcycles.

electrical question - 2 generators/alternators
 

Thanks for the Info. I appreciate it.
I agree that I will need diodes, but let me rephrase the question:
Will both generators be charging the bank at the same time? In other words,
if one generator is putting out 20 amps at 14 volts, and the other is
putting out 10 amps at 14 volts, does that mean that the batteries will
"see" 30 amps at 14 volts? Will the batteries "see" only 20 amps? Only 10
amps? What happens when 1 generator is putting out 20 amps at 14 volts,
while the other is putting out 20 amps at 13.9 volts?

Mark

"Rick Cortese" wrote in message
.net...
Mark Newcomb wrote:
I have a question that I would appreciate an answer to from anyone who
has a clue.

My question is this: can you have 2 generators (or alternators) charging
the same battery bank at the same time? For example, if I have 2 wind
generators will they both charge my house bank simultaneously? Or, can
only one generator/alternator be in use at one time?

IMO: Could cause problems. It would be safer if you put at least one
blocking diode or rectifier in the circuit. Maybe a selenium rectifiers
that is rated at current qs to handle the generators output like those
used in motorcycles.

electrical question - 2 generators/alternators
 

From an electronics point of view the alternator with the highest 'voltage' will
be doing all the work the other will be just free-wheeling. If they are the
same voltage, one will 'assist' the other but not to the total of the both.

I expect that the 20A alternator will do most of the work, the 10A will simply
pick up speed till it starts to get loaded at the same voltage as the 20A
alternator

There are always variables, for example, the 10A unit may be more efficient at
low wind & will start charging first but the 20A unit will take over when the
wind picks up. (not a bad combination really)

PS, wind alternators 'should' have isolation diode already built in even if its
just the rectifier diodes.

On Thu, 04 May 2006 20:01:31 GMT, "Mark Newcomb"
wrote:

Thanks for the Info. I appreciate it.
I agree that I will need diodes, but let me rephrase the question:
Will both generators be charging the bank at the same time? In other words,
if one generator is putting out 20 amps at 14 volts, and the other is
putting out 10 amps at 14 volts, does that mean that the batteries will
"see" 30 amps at 14 volts? Will the batteries "see" only 20 amps? Only 10
amps? What happens when 1 generator is putting out 20 amps at 14 volts,
while the other is putting out 20 amps at 13.9 volts?

Mark

"Rick Cortese" wrote in message
k.net...
Mark Newcomb wrote:
I have a question that I would appreciate an answer to from anyone who
has a clue.

My question is this: can you have 2 generators (or alternators) charging
the same battery bank at the same time? For example, if I have 2 wind
generators will they both charge my house bank simultaneously? Or, can
only one generator/alternator be in use at one time?

IMO: Could cause problems. It would be safer if you put at least one
blocking diode or rectifier in the circuit. Maybe a selenium rectifiers
that is rated at current qs to handle the generators output like those
used in motorcycles.

--

Australia isn't "down under", it's "off to one side"!


www.cobracat.com (home of the Australian Cobra Catamaran)
http://groups.yahoo.com/group/cobra-cat/

electrical question - 2 generators/alternators
 

Thank you so much. Now I understand.

Mark


"Stan Blazejewski" wrote in message
...
From an electronics point of view the alternator with the highest
'voltage' will
be doing all the work the other will be just free-wheeling. If they are
the
same voltage, one will 'assist' the other but not to the total of the
both.

I expect that the 20A alternator will do most of the work, the 10A will
simply
pick up speed till it starts to get loaded at the same voltage as the 20A
alternator

There are always variables, for example, the 10A unit may be more
efficient at
low wind & will start charging first but the 20A unit will take over when
the
wind picks up. (not a bad combination really)

PS, wind alternators 'should' have isolation diode already built in even
if its
just the rectifier diodes.

On Thu, 04 May 2006 20:01:31 GMT, "Mark Newcomb"

wrote:

Thanks for the Info. I appreciate it.
I agree that I will need diodes, but let me rephrase the question:
Will both generators be charging the bank at the same time? In other
words,
if one generator is putting out 20 amps at 14 volts, and the other is
putting out 10 amps at 14 volts, does that mean that the batteries will
"see" 30 amps at 14 volts? Will the batteries "see" only 20 amps? Only
10
amps? What happens when 1 generator is putting out 20 amps at 14 volts,
while the other is putting out 20 amps at 13.9 volts?

Mark

"Rick Cortese" wrote in message
nk.net...
Mark Newcomb wrote:
I have a question that I would appreciate an answer to from anyone who
has a clue.

My question is this: can you have 2 generators (or alternators)
charging
the same battery bank at the same time? For example, if I have 2 wind
generators will they both charge my house bank simultaneously? Or, can
only one generator/alternator be in use at one time?

IMO: Could cause problems. It would be safer if you put at least one
blocking diode or rectifier in the circuit. Maybe a selenium rectifiers
that is rated at current qs to handle the generators output like those
used in motorcycles.

--

Australia isn't "down under", it's "off to one side"!


www.cobracat.com (home of the Australian Cobra Catamaran)
http://groups.yahoo.com/group/cobra-cat/

electrical question - 2 generators/alternators
 

Mark Newcomb wrote:
Thanks for the Info. I appreciate it.
I agree that I will need diodes, but let me rephrase the question:
Will both generators be charging the bank at the same time? In other words,
if one generator is putting out 20 amps at 14 volts, and the other is
putting out 10 amps at 14 volts, does that mean that the batteries will
"see" 30 amps at 14 volts? Will the batteries "see" only 20 amps? Only 10
amps? What happens when 1 generator is putting out 20 amps at 14 volts,
while the other is putting out 20 amps at 13.9 volts?

I would bet yes since in the discharged state the both chargers will be
looking at less then ~14V so they will be at maximum charging rate/load.

When the battery are near completely charged one or the other charger
will shut off first depending on its set point. The rectifiers will
prevent one generator from acting like a load/being driven by the other
charger. It may need a bit more in the circuits to get it to work with
the voltage drop across the rectifier. Probably a low Ohm high Wattage
resistor would work. Something like a 10 Ohm 20 Watt or 20 Ohm 10 Watt
may do it.

electrical question - 2 generators/alternators
 

Rick Cortese wrote:
Mark Newcomb wrote:

I have a question that I would appreciate an answer to from anyone who
has a clue.

My question is this: can you have 2 generators (or alternators)
charging the same battery bank at the same time? For example, if I
have 2 wind generators will they both charge my house bank
simultaneously? Or, can only one generator/alternator be in use at
one time?


IMO: Could cause problems. It would be safer if you put at least one
blocking diode or rectifier in the circuit. Maybe a selenium rectifiers
that is rated at current qs to handle the generators output like those
used in motorcycles.

There is no problem that I know of. My boat (and several hundred
sister ships) has twin engine that feed a house bank with no diodes,
etc. In addition, many have solar panels and/or wind generators that
are always connected. Further, they use a combiner to also charge two
starting batteries, and it all magically works.

That said, there are three regulators that are trying to sense the
battery voltage and will see the other Voltage sources. I have little
problem with this, because the most aggressive regulator (i.e. the
highest Voltage) is on the larger alternator. The small alternator
normally shuts off and is hardly used - its still has the original
belt after 6 seasons. I don't really want to get the full 100 Amps
when I'm powering, since that overloads my small Yanmar 2GM. And I
don't expect much from the solar system while an engine is running.

electrical question - 2 generators/alternators
 

Jeff wrote:
Rick Cortese wrote:

Mark Newcomb wrote:

I have a question that I would appreciate an answer to from anyone
who has a clue.

My question is this: can you have 2 generators (or alternators)
charging the same battery bank at the same time? For example, if I
have 2 wind generators will they both charge my house bank
simultaneously? Or, can only one generator/alternator be in use at
one time?



IMO: Could cause problems. It would be safer if you put at least one
blocking diode or rectifier in the circuit. Maybe a selenium
rectifiers that is rated at current qs to handle the generators output
like those used in motorcycles.


There is no problem that I know of. My boat (and several hundred sister
ships) has twin engine that feed a house bank with no diodes, etc. In
addition, many have solar panels and/or wind generators that are always
connected. Further, they use a combiner to also charge two starting
batteries, and it all magically works.

Alternators 'cept the solar panel which probably has blocking diodes
which have diodes built in. The OP may have misspoke but he included
generator.

I'm just old enough to remember old style generators that we used to
hook up to 12V batterys to see them run. I seem to recall my family had
a pit bike type minibike made out of a 12V lead acid automotive battery
hooked to a generator/drive motor for riding around the farm *but* I am
really foggy on that one. My memory of things in the 50's is really bad.

electrical question - 2 generators/alternators
 

Rick Cortese wrote:
Jeff wrote:
There is no problem that I know of. My boat (and several hundred
sister ships) has twin engine that feed a house bank with no diodes,
etc. In addition, many have solar panels and/or wind generators that
are always connected. Further, they use a combiner to also charge two
starting batteries, and it all magically works.


Alternators 'cept the solar panel which probably has blocking diodes
which have diodes built in. The OP may have misspoke but he included
generator.

I'm just old enough to remember old style generators that we used to
hook up to 12V batterys to see them run. I seem to recall my family had
a pit bike type minibike made out of a 12V lead acid automotive battery
hooked to a generator/drive motor for riding around the farm *but* I am
really foggy on that one. My memory of things in the 50's is really bad.

Is your point that without blocking one generator would try to run the
other as a motor? Interesting point, although it doesn't apply to
alternators.

I do remember motor/generators; my first boat had a Palmer one
cylinder gas engine (about 6 HP?) with a starter/generator and magneto
ignition.

electrical question - 2 generators/alternators
 

Jeff wrote:
Rick Cortese wrote:

Jeff wrote:

There is no problem that I know of. My boat (and several hundred

sister ships) has twin engine that feed a house bank with no diodes,
etc. In addition, many have solar panels and/or wind generators that
are always connected. Further, they use a combiner to also charge
two starting batteries, and it all magically works.



Alternators 'cept the solar panel which probably has blocking diodes
which have diodes built in. The OP may have misspoke but he included
generator.

I'm just old enough to remember old style generators that we used to
hook up to 12V batterys to see them run. I seem to recall my family
had a pit bike type minibike made out of a 12V lead acid automotive
battery hooked to a generator/drive motor for riding around the farm
*but* I am really foggy on that one. My memory of things in the 50's
is really bad.


Is your point that without blocking one generator would try to run the
other as a motor? Interesting point, although it doesn't apply to
alternators.

Right. More info then you probably want or need, but the old systems
only used relays to isolate the generator when a set point was reached.
The phase+DC was picked off permanent magnet generator by brushes on
the armature.

I admit it probably doesn't apply but I have seen a lot of equipment
that is cheaply designed so it can hit a price point. Things from arc
welders to battery chargers that limit current by the amount of iron in
the transformer rather then real current limiting circuitry. I wouldn't
trust anything until it has been checked to see if blocks current.

electrical question - 2 generators/alternators
 

Here is the pertimnant part of my original question. If I had 2 wind
generators (for example) and wanted to use them to both charge the batteries
while sailing, would I have to "split" the house bank so that I was actually
using both generators at the same time. The answer I receieved (I think)
points to "yes, you would split the house batteries during charging, with
each generator charging a separate bank."
"Rick Cortese" wrote in message
et...
Jeff wrote:
Rick Cortese wrote:

Jeff wrote:

There is no problem that I know of. My boat (and several hundred

sister ships) has twin engine that feed a house bank with no diodes,
etc. In addition, many have solar panels and/or wind generators that
are always connected. Further, they use a combiner to also charge two
starting batteries, and it all magically works.



Alternators 'cept the solar panel which probably has blocking diodes
which have diodes built in. The OP may have misspoke but he included
generator.

I'm just old enough to remember old style generators that we used to
hook up to 12V batterys to see them run. I seem to recall my family had
a pit bike type minibike made out of a 12V lead acid automotive battery
hooked to a generator/drive motor for riding around the farm *but* I am
really foggy on that one. My memory of things in the 50's is really bad.


Is your point that without blocking one generator would try to run the
other as a motor? Interesting point, although it doesn't apply to
alternators.

Right. More info then you probably want or need, but the old systems only
used relays to isolate the generator when a set point was reached. The
phase+DC was picked off permanent magnet generator by brushes on the
armature.

I admit it probably doesn't apply but I have seen a lot of equipment that
is cheaply designed so it can hit a price point. Things from arc welders
to battery chargers that limit current by the amount of iron in the
transformer rather then real current limiting circuitry. I wouldn't trust
anything until it has been checked to see if blocks current.

electrical question - 2 generators/alternators
 

Mark Newcomb wrote:
Here is the pertimnant part of my original question. If I had 2 wind
generators (for example) and wanted to use them to both charge the batteries
while sailing, would I have to "split" the house bank so that I was actually
using both generators at the same time. The answer I receieved (I think)
points to "yes, you would split the house batteries during charging, with
each generator charging a separate bank."
"Rick Cortese" wrote in message
et...


I don't think that is necessarily so. You should be asking this
question of the wind generator people, since they would understand how
their particular devices work. As I've said, I have all of my
charging sources feeding the house bank, and the only noticeable
affect is that regulators (there are three in the system) would
sometimes shut off and defer to the strongest source. This, however
has never been a problem worth solving, its only a curiosity, since I
really don't care about 2 Amps of solar power when a 100 Amp
alternator is running. With two identical wind generators, there
could be an issue if each had a regulator that would be affected by
the other. This issue might not exist, or it could be solved with a
dual source regulator (there are some on the market). Splitting the
house bank into two sidesteps the issue, but then you have two banks
at differing charge states, which is less than optimum. Since the
wind and solar systems are "set it and forget it," designing the
system so that you have to monitor charge and flip switches is not
desirable.

electrical question - 2 generators/alternators
 

Mark Newcomb wrote:
Here is the pertimnant part of my original question. If I had 2 wind
generators (for example) and wanted to use them to both charge the batteries
while sailing, would I have to "split" the house bank so that I was actually
using both generators at the same time. The answer I receieved (I think)
points to "yes, you would split the house batteries during charging, with
each generator charging a separate bank."
"Rick Cortese" wrote in message
et...

I'm pretty sure you don't have to split them.

I can't recall the right term, something like excited field alternator.
Anyway the wind generators are actually alternators with a magnet in
them to get away from the problem of completely discharged batteries.

All the circuitry to prevent reverse flow is integral in their design.
That is unless you happened to pick up a couple some farmer made out of
old automotive generators.grin

If you are using any wind generator that is currently marketed for the pleasure boat industry and that wind generator has not been modified this will be the result of connecting multiple generators in parallel:

As long as the voltage of the bank of batteries being charged is below the free wheeling voltage* of the generators the generators will charge the batteries in proportion to their output. i.e., #1 gen = 20A #2 gen = 10A then #1 will supply 66% of the total charging current while #2 supplies 33%.

If the voltage of the batteries being charged ever reaches the free wheeling voltage of one of the generators then that generator will not contribute to the charging until the battery voltage falls below the free wheeling voltage again.

free wheeling voltage* is the voltage of the generator measured with it disconnected from the batteries.