I have a 22' Chaparral with a Merc 350 300HP. I do a lot of lake
boating, long days, and would like to have a reserve battery to start
the boat in case the primary drains while docked or just for
emergency.

I'd like to wire in a combiner and switch as show here
http://www.skingcompany.com/manuals/C50.pdf

I am not sure what amp rating I need for the combiner and switch. Can
someone help with this. I don't care about saving pennies, want the
best system for safety.

Thanks,
Bob

"Bob" wrote in message
...
I have a 22' Chaparral with a Merc 350 300HP. I do a lot of lake
boating, long days, and would like to have a reserve battery to start
the boat in case the primary drains while docked or just for
emergency.

I'd like to wire in a combiner and switch as show here
http://www.skingcompany.com/manuals/C50.pdf

I am not sure what amp rating I need for the combiner and switch. Can
someone help with this. I don't care about saving pennies, want the
best system for safety.

Thanks,
Bob

Get a Guest Dual battery switch, West Marine or any other marine supplier.
A 50 amp combiner as you do not have a 100 amp alternator likely on a 350
cid engine. The 50 amp combiner is $80 at West, hook the two batteries
together with the combiner, I did it at the Guest switch. Instructions in
the combiner. I run my electronics off the second battery and added a
single battery switch in the feed to the fuse panel, so I can shut off all
the power in the boat. You can add a small switch in the combiner to shut
it off, if you want to charge only one battery. I did not.

Bill,

Thanks, I checked Mercury's website and the engine
has a 65 amp alternator
http://www.mercurymarine.com/350_mag_mpi_sd_-_300_hp

In this case, I should probably get something larger
than the 50 amp, do you concur?

Bob


"Calif Bill" wrote:


"Bob" wrote in message
.. .
I have a 22' Chaparral with a Merc 350 300HP. I do a lot of lake
boating, long days, and would like to have a reserve battery to start
the boat in case the primary drains while docked or just for
emergency.

I'd like to wire in a combiner and switch as show here
http://www.skingcompany.com/manuals/C50.pdf

I am not sure what amp rating I need for the combiner and switch. Can
someone help with this. I don't care about saving pennies, want the
best system for safety.

Thanks,
Bob

Get a Guest Dual battery switch, West Marine or any other marine supplier.
A 50 amp combiner as you do not have a 100 amp alternator likely on a 350
cid engine. The 50 amp combiner is $80 at West, hook the two batteries
together with the combiner, I did it at the Guest switch. Instructions in
the combiner. I run my electronics off the second battery and added a
single battery switch in the feed to the fuse panel, so I can shut off all
the power in the boat. You can add a small switch in the combiner to shut
it off, if you want to charge only one battery. I did not.



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But how many times are you putting 65 amps into the battery.
Bill

"Bob" wrote in message
...
Bill,

Thanks, I checked Mercury's website and the engine
has a 65 amp alternator
http://www.mercurymarine.com/350_mag_mpi_sd_-_300_hp

In this case, I should probably get something larger
than the 50 amp, do you concur?

Bob


"Calif Bill" wrote:


"Bob" wrote in message
.. .
I have a 22' Chaparral with a Merc 350 300HP. I do a lot of lake
boating, long days, and would like to have a reserve battery to start
the boat in case the primary drains while docked or just for
emergency.

I'd like to wire in a combiner and switch as show here
http://www.skingcompany.com/manuals/C50.pdf

I am not sure what amp rating I need for the combiner and switch. Can
someone help with this. I don't care about saving pennies, want the
best system for safety.

Thanks,
Bob

Get a Guest Dual battery switch, West Marine or any other marine
supplier.
A 50 amp combiner as you do not have a 100 amp alternator likely on a 350
cid engine. The 50 amp combiner is $80 at West, hook the two batteries
together with the combiner, I did it at the Guest switch. Instructions
in
the combiner. I run my electronics off the second battery and added a
single battery switch in the feed to the fuse panel, so I can shut off
all
the power in the boat. You can add a small switch in the combiner to
shut
it off, if you want to charge only one battery. I did not.



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Who knows, once would be too many though. I dont skimp
pennies hoping that wouldnt happen!

Bob


"Calif Bill" wrote:

But how many times are you putting 65 amps into the battery.
Bill

"Bob" wrote in message
.. .
Bill,

Thanks, I checked Mercury's website and the engine
has a 65 amp alternator
http://www.mercurymarine.com/350_mag_mpi_sd_-_300_hp

In this case, I should probably get something larger
than the 50 amp, do you concur?

Bob


"Calif Bill" wrote:


"Bob" wrote in message
.. .
I have a 22' Chaparral with a Merc 350 300HP. I do a lot of lake
boating, long days, and would like to have a reserve battery to start
the boat in case the primary drains while docked or just for
emergency.

I'd like to wire in a combiner and switch as show here
http://www.skingcompany.com/manuals/C50.pdf

I am not sure what amp rating I need for the combiner and switch. Can
someone help with this. I don't care about saving pennies, want the
best system for safety.

Thanks,
Bob

Get a Guest Dual battery switch, West Marine or any other marine
supplier.
A 50 amp combiner as you do not have a 100 amp alternator likely on a 350
cid engine. The 50 amp combiner is $80 at West, hook the two batteries
together with the combiner, I did it at the Guest switch. Instructions
in
the combiner. I run my electronics off the second battery and added a
single battery switch in the feed to the fuse panel, so I can shut off
all
the power in the boat. You can add a small switch in the combiner to
shut
it off, if you want to charge only one battery. I did not.



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I don't know about the amps for your situation. I'll let you and
others think that one through.

One thing though. The picture in your link shows the wiring panel
coming off the #2 part of the switch. I prefer to have my wiring
panel come off the COMMON (not common-ground, but common-
positive) part of the switch. That way I can decide which battery I
want to be using for my panel.

Another thing. Some A/B/ALL switches have a "make before
break" connection. That means that as you switch from, say,
battery A to battery B - that battery B will be connected to the
circuit BEFORE the connection to battery A is broken. This
prevents a condition where NO battery is connected for a
second. This prevents damage to your altenator. It costs a few
bucks more, but I think it's a good idea.

Gary

"Bob" wrote in message
...

I am not sure what amp rating I need for the combiner and switch. Can
someone help with this. I don't care about saving pennies, want the
best system for safety.


Well, if money is no object, get a combiner that has more capacity than the
maximum output of the alternator.

If you would rather spend your money on more useful stuff, the 50 amp model
you have selected will work fine. Note that the ratings on this unit are 50
amps continuous, and 100 amps for 5 minutes. It is very unlikely that you
would ever end up charging the backup battery at more than 50 amps, and
unless the battery is very large or you had multi-stage regulator on the
alternator I don't think you could charge it at more than 50 amps for more
than 5 minutes. Even if you did, the combiner has a thermal shutdown that
would protect it.

Where you could get into trouble with such a device is if you have two
battery systems, such as a cabin battery and starting battery. If your
cabin system is using a lot of current (such as running an inverter) and the
engine is running then you could end up passing the full alternator output
to the cabin circuit via the combiner. If the second battery is just for
reserve, then you shouldn't have any issue.

As for the switch, get a good one. Since all your starting current has to
pass through this switch at all times, you don't want it to cause you any
problems. Keep the cables from the batteries to the switch and switch to
engine as short as possible.

Rod