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Catalina/Capri 25/250 Sailor's Forums

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Adding a Battery Selector and A Voltmeter

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Scott Shephard
Deckhand

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USA
22 Posts

Initially Posted - 05/15/2013 : 03:34:14

I have spent two or three hours searching but my conceptual confusion about 12 volt systems is getting in the way of figuring my problem out. So here's the problem:

I have shore power running through a Guest 2610 Two Output Charger to one battery. I also have a Johnson 9.9 motor with the alternator connections going directly to the battery terminals.

I want to add a second battery, a Blue Sea 6007 battery selector switch and either an analog or digital voltmeter.

The Guest 2610 owner's manual makes it pretty simple to understand how to add a second battery. (Remove red jumper cable, etc.)

What I don't understand are these things:

Where in relation to the Guest charger do I put the battery switch?
Where in all of this do I put the wires to the voltmeter?
Do I leave the Johnson alternator wires attached to the one battery?
Do I have to do anything more with wiring to the fuse block and 15 amp fuse installed with the Guest charger? (Right now there are three positive wires running to it)

I'm guessing there are many on this forum who have this exact set-up who might be willing to share a simple explanation/diagram/video of how this is done. Or perhaps a link to an article that explains all of this.

Thanks!

Edited by - Scott Shephard on 05/15/2013 07:54:11

OLarryR
Master Marine Consultant

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USA
3441 Posts

Response Posted - 05/15/2013 : 20:56:44

Scott,

The Association has the boat manuals with electrical sketches accessible from the left side of the screen. The sketch for the Cat 25 seemed to have a better schematic to illustrate what you requested, so I have provided the link below. As far as the charger goes, I also have a charger with separate leads for each battery and so I have the leads hooked up directly to each battery terminal - Not thru the battery switch since the charger is set up to independently charge each battery.

In regards to the outboard, there are a number of ways to hook it up thru the battery switch depending on how you want it to charge the battery(ies) and/or how you want to start the outboard. Some may have the outboard off of only one battery and so then the positive wire is hooked up thru the battery switch to that one battery. Those that do it this way, then generally use the other battery for their household loads (ie. Cabin lights, etc). Another way to hook it up is for the positive wire to the battery switch combined terminal, then you can utilize the switch in the #1, #2 or combined position for starting the outboard and/or charging a single or both batteries. The negative is hooked up to one battery with a jumper to the battery's negative terminal. I generally leave my battery switch in the "Combined" position all the time and so I am sort of utilizing both batteries as one battery.

Actually, there is a better way to do hookups for two battery banks to ensure that one battery does not drag the other battery down and that is to utilize a battery "Isolator" or "Combiner". The combiner is probably the better of the two. There is info on the web, etc on the benefits of using an isolator or combiner but it does at least for the initial hook up, complicate things. So far, I have not gone the isolator or combiner route but I keep thinking about it. Also, in regards to the above, there are benefits and negatives with always using the batteries with the battery switch left in the Combined position. Main benefit is that you do not have to give any thought as to what battery the outboard has been charging - It's charging both. Negative is that if one battery is weaker than the other, it tends to draw down the other battery and during outboard charging, the better battery does not get full benefit of the charge.

http://catalina-capri-25s.org/manbro/pictures/4-2-5.gif

Edited by - OLarryR on 05/15/2013 21:00:52

Scott Shephard
Deckhand

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USA
22 Posts

Response Posted - 05/16/2013 : 00:43:27

Perfect! Thanks. I have read about the battery isolators but my sense is that making one battery available for engine starting is more critical to boats with bigger engines. In my case, the Johnson 9.9 has a pull start and is very easy to start without electricity.

My two new gel batteries arrive from West Marine today and I am excited about putting the finishing touches on getting my boat ready for launch after what has been a fairly long winter in South Dakota.

Thanks again.

SS

Edited by - on

TakeFive
Master Marine Consultant

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2272 Posts

Response Posted - 05/16/2013 : 05:31:15

If you are starting over with two brand new identical batteries, why not just connect them in parallel and not have a switch? The switch and/or isolator are generally used to keep a starter battery "fresh" for starting the motor. But as you pointed out, with our boats pulling the cord on the outboard is an easy alternative if your starter battery dies. It much different than if you had a large inboard diesel.

The only argument against hooking them up in parallel is that if one battery goes bad, it will likely cause the other one to go bad also. But think of it this way: By connecting the batteries in parallel, you are reducing the discharge cycle of each battery by half, which reduces the chance of either battery going bad. Even Larry mentioned that he pretty much leaves the switch on "both" which is the same as not having the switch at all.

Of course, if you had an emergency and needed to disconnect one battery because it went bad, you could disconnect it manually.

Frankly, just having the switch creates a risk that you (or an untrained passenger) could momentarily turn the switch to "0" while the motor is running, which will create a significant repair bill on your outboard.

So I say keep it simple and just connect the batteries in parallel.

DISCLAIMER: I do not have two batteries currently, so I am not speaking from actual experience. But I have two identical batteries in my basement (connected in parallel) that I use for other things, and if I took a long cruise that needed two batteries, I would follow this suggestion on my C250.

PS - For a voltmeter, I just plug one of these in (click for link):

<center>[url="http://www.walmart.com/ip/Equus-Innova-3721-Battery-and-Charging-System-Monitor/15137663"]

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Edited by - TakeFive on 05/16/2013 05:33:56

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The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.