I recently purchased a new (used) boat. It has a 350 merc and uses 2
batteries.
I think 1 is a starting battery and the other is a deep cycle w/
cranking amps. There is a switch for the batteries to select #1, #2,
or both. No manual.

I am not familiar with this setup.

1 - why is this system utilized (why not just 1 battery?) and what is
the proper operation of this system?
2 - should I always have it switched to "both" so both batteries get
charged when running? what is the preferred switch scenario?
3- which battery is better to run the electronics to? (I imagine the
deep cycle.)

Thanks for the advice.
-mark

Mark,

Except for trolling motors the primary purpose is redundancy. It's nice to
have a backup.

Both of my batteries are starting type. When starting and running I use both.
Swithching while running is not recommended. Damages the alternator.

While fishing or at anchor I switch to Batt #2 which powers the VHF,
sounder/GPS/Chart, and bilge pump.

Now and then I start and run on Batt #2 or Batt #1 just to be sure either have
the capacity to start the O/B.

The batteries will be five years old in April so I'll probably replace them. I
hate having dead batteries out in the middle of nowhere with no boat in sight.
Batteries are cheap tows are not.

Butch

Mark wrote: snip 1 - why is this system utilized (why not just 1 battery?)
and what is
the proper operation of this system?
2 - should I always have it switched to "both" so both batteries get
charged when running? what is the preferred switch scenario?
3- which battery is better to run the electronics to? (I imagine the
deep cycle.)snip

On 4 Jan 2004 07:36:04 -0800, (mark s) wrote:
I recently purchased a new (used) boat. It has a 350 merc and uses 2
batteries.
I think 1 is a starting battery and the other is a deep cycle w/
cranking amps. There is a switch for the batteries to select #1, #2,
or both. No manual.

I am not familiar with this setup.

1 - why is this system utilized (why not just 1 battery?) and what is
the proper operation of this system?
2 - should I always have it switched to "both" so both batteries get
charged when running? what is the preferred switch scenario?
3- which battery is better to run the electronics to? (I imagine the
deep cycle.)
==============================================

The answer(s) should certainly be in the FAQ file if we only had one.

Here's the short and simple version:

The second battery is there primarily as a spare in case the first one
gets run down too far to start the engine.

There are exceptions to everything but as a general rule you should
NEVER switch batteries with the engine running. This can lead to
instant alternator failure under some conditions.

If you need battery 2 to start the engine, set the switch to #2 and
leave it there until the engine is warmed up and easy to start. Then,
stop the engine, switch to BOTH and restart. It's a good idea to put
battery 1 on a charger when you return to make sure it's topped off
properly.

My personal preference is for both batteries to be marine deep cycle
although some will disagree.

I occassionally start the engine with the switch in the BOTH position
to ensure that battery 2 stays charged. If you do this, you should
immediately switch back to battery 1 after you stop the engine.

Nothing except the primary bilge pump should be wired directly to a
battery. Everything else, including electronics, should connect
through the battery switch. One good reason for this is to ensure
that when you turn off the battery switch, EVERYTHING goes off.
Otherwise you risk leaving something on accidently which drains (and
ruins) your batteries.

That's the short and simple version. There are gadgets available to
automate charging of the #2 battery but that leads to a lengthy
discussion of pros, cons and risks. In any case it's a good idea to
have an accurate voltmeter and/or a low voltage alarm warning.

Using the strategy outlined above, battery 1 will get most of the
heavy usage and will need to be replaced more frequently than #2. My
suggestion would be to replace it at the first sign that it's no
longer holding a charge as long as it used to. In an ideal world you
should never use the #2 batt for anything but an emergency. If you
routinely discharge #1 to the point where it will not start the
engine, you will experience very short battery life. The best
solution is to get a bigger #1 battery with more capacity.

snip
The answer(s) should certainly be in the FAQ file if we only had one.
snip

We do; see:

http://www.faqs.org/faqs/boats-faq/part1/index.html

http://ejo.univ-lyon1.fr/faq/by-news...rec/rec.boats/

http://www.newsville.com/cgi-bin/getfaq?rec.boats

http://omicron.felk.cvut.cz/FAQ/articles/n1037.html

http://faqs.jmas.co.jp/FAQs/boats-faq/

Also, see the boats of rec.boats at:

http://thebayguide.com/rec.boats/

Mark Browne

Mark, you're right of course but these so called FAQs have not been
updated in years, are VERY poorly organized, and contain a lot of
misleading or out of date, i.e., "wrong" information. I just spent
about 20 minutes pretending to wear my newbie hat, and tried to find a
reasonable answer to the aforementioned battery switching question.
The answer may be in there but not before my patience ran out.

OK, so much for criticism, here's my vision of what the FAQ should be
for what it's worth: It should be HTML based with appropriate
hyperlinks to related or more detailed information; The table of
contents should be hyperlinked; It should be searchable by keyword;
It should be periodically updated as new or better information becomes
available; There should be a review process to sift out, or properly
annotate, controversial points of view.

Just my 2 cents worth, now we need some volunteers :-)

================================================== ==

On Sun, 04 Jan 2004 17:12:11 GMT, "Mark Browne"
wrote:
snip
The answer(s) should certainly be in the FAQ file if we only had one.
snip

We do; see:

http://www.faqs.org/faqs/boats-faq/part1/index.html

http://ejo.univ-lyon1.fr/faq/by-news...rec/rec.boats/

http://www.newsville.com/cgi-bin/getfaq?rec.boats

http://omicron.felk.cvut.cz/FAQ/articles/n1037.html

http://faqs.jmas.co.jp/FAQs/boats-faq/

Also, see the boats of rec.boats at:

http://thebayguide.com/rec.boats/

Mark Browne

Those of us who have big stereos and spend most of the time rafted off use
the #2 battery while at anchor.
Those big amps will pull a battery down in no time flat.
We anchor/raft off and throw the switch to #2.
It's also nice to have a second as a backup, but have never needed it for
starting.


"JDavis1277" wrote in message
...
Mark,

Except for trolling motors the primary purpose is redundancy. It's nice
to
have a backup.

Both of my batteries are starting type. When starting and running I use
both.
Swithching while running is not recommended. Damages the alternator.

Lots of good reasons mentioned here about why you have two batteries. I
like a starting battery like you have in your car for starting and a
deep cycle for other things like trolling motors, stereo, refrigeration,
anchor lights, etc. This is the kind of equipment that draws your
battery down farther and a deep cycle doesn't mind this as much as a car
battery. Car batteries are also cheaper.

I like to connect mine with a combiner (not an isolator) that you can
get at West for $70 and hook up in 15 minutes. It sends power to
whichever battery needs it without messing with that A/B switch. Im
going on 5 years on my set and they still work well. I also don't take
them out of the boat here in Minnesota (where it is 0 right now), but
leave them on a 600 milliamp maintainer instaed, but that's another topic.

Capt. Jeff

"mark s" wrote in message

I think 1 is a starting battery and the other is a deep cycle w/cranking
amps.

As I understand it, a starting battery is setup to deliver lots
of amps over a short time (as in when starting). A deep cycle
or "house" battery is setup to be better at providing a lower amp
load for a long period of time (as then running electronics without
the engine running). Each can do the other's job, but not as efficiently
and with more damage to the battery. So "deep cycle" with "craking amps"
is, I believe, not quite correct.


1 - why is this system utilized (why not just 1 battery?) and what is
the proper operation of this system?

This system is there so that when you are running electronics without
the engine running (say when fishing, on anchor, or maybe at the dock)
you will be draining the deep-cycle/house battery. This battery is
made for this type of discharge. More importantly, you will not
accidentially drain down your starting battery.

Assuming #1 is starting battery and #2 is the house battery:
Normally Start and Run on "both". This allows both batteries
to remain charged up. Then when you stop the engine switch to
battery #2. This way only #2 will be drained. When ready to
start flipping to both should allow you to start the engine. If not,
you can flip to just #1 to start the engnie. When you are off the boat
flip to OFF.

As others have said, changing the switch position when then the
engine is running could cause problems. This is because the
altenator is putting out power but for a moment when you flip
the switch there is no battery to "take up" that power.

However, some altenator / power systems regulate for this. Also,
you can buy a 1/2/BOTH/OFF switch that is a "make before break"
switch. This means it makes the connetion to the next battery
before breaking the connection to the previous one. Example: When
switching from #1 to #2 it would connect to #2 before breaking
the conenction with #1. With this type of switch it's not a problem.

See: http://tinyurl.com/27u45
Note that in the description blurb they say "We strongly recommend field
disconnect battery switches (or failsafe diodes) to eliminate the chance
of alternator damage due to inadvertent switching."


Also, some power generation systems do not put out any power
until you reach a certain RPM on the engine. So switching at low
RPMs (idle) may not be a problem.

The safest rule is not to switch with the engine running...but that may
or may not be necessary on your system.

2 - should I always have it switched to "both" so both batteries get
charged when running? what is the preferred switch scenario?

Answered above. Generally:
BOTH when starting & running
#2 when engine is off but you are running electronics
OFF when you leave the boat
#1 only to start if BOTH does not work.


3- which battery is better to run the electronics to? (I imagine the
deep cycle.)

Deep cycle.

Also, many people just use two of the same battery. They get
two "dual-purpose" batteries. This is also good in that both
batteries have the same charging characteristics.

Another note:
As another poster mentioned, there are other things you can add
to your system. I have a "battery combiner" along with my 1/2/BOTH
switch. The Battery Combiner (BC) makes a connection between #1
and #2 when the charging system is putting out 13.3 volts or more.

With this setup I just flip the switch from OFF to either #1 or #2
and then do whatever I want (start the boat, stop, use power, etc.)
When the engine is running the charging system is putting out
13.3 or more volts and BOTH batteries get charged up. If I shut
off the engine I'm only drawing from the one battery. If ever
I drain that battery, I can always switch to the other to start the boat.

This setup means I don't have to remember to flip the switch except
to turn it on when I get in the boat and off when I leave it. I have two
of the same batteries, so I just alternate between whether I flip the
switch to #1 or #2.

Here's a link to a BC:
http://tinyurl.com/2g3ut


Thanks for the advice.
-mark

Hope that helps.
Gary

Gary
when I saw the question "Why 2 batteries on Boat?" and saw that you
answered, all I could think of was why ONLY 2 batteries on a boat? I
think you remember the days when 3 or 4 or more batteries on the boat
or in the apartment charging wasn't enough. Anyway Happy New Year
Buddy
I am so Jonesing to get my boat back in the water, and it has only
been about a week now that it has been on land.
Talk to you soon