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Author Topic:   Wiring schematic for dual battery system
Nigel posted 05-23-2002 09:28 PM ET (US)   Profile for Nigel   Send Email to Nigel  
Does anyone have a wiring schematic which shows how to install a dual battery system for a single outboard using a switch which has 1,2, both and off positions? [Requested email communication--we do not endorse turning these public discussions into private email. The purpose of the website is to organize information available to all and to have public discussions--jimh]


seagull posted 05-24-2002 08:55 AM ET (US)     Profile for seagull  Send Email to seagull     
Go to Guest site and they have all the differnet types of battery setups. Link below will gwt you there.

[Dead link has been removed.]

jimh posted 05-24-2002 09:52 AM ET (US)     Profile for jimh  Send Email to jimh     
The wiring diagrams shown at the GUEST website are not directly applicable to outboard engine installations for several reasons.

The GUEST wiring suggestions often make use of distinct wiring circuits which interconnect the BATTERY, the ALTERNATOR, and the STARTER MOTOR to the SWITCH and ISOLATOR. This type of wiring is great for inboard engines, but it really is not applicable to ouboard engines.

Outboard engines usually contain all the interconnections between ALTERNATOR and STARTER MOTOR under the cowling of the engine, and it is hardly possible to imagine someone rewiring the internals of their outboard, bringing out separate leads for the starter and the alternator, and interconnecting them in some of the arrangements shown by Guest.

triblet posted 05-24-2002 11:01 AM ET (US)     Profile for triblet  Send Email to triblet     
The West Marine catalog has a decent schematic.

And didn't jimh post an article on it?


hauptjm posted 05-24-2002 11:03 AM ET (US)     Profile for hauptjm    
jimh, your article on the 2bat/2engine rig was superb. Maybe we can enlist your expertise on the 2/1 setup. And if you're really getting fancy, add an on-board charger.

I've got a weird system on my boat. I've got two batteries for the single engine and a third battery just for the console (electronics). All are connected to an onboard charger. The engine keeps the two in the rear charged and the single in the console is only charged by the charger. I know it sounds weird but it works. I have never run the electronics battery down to 0, and I always have fresh batteries to start the Johnny. One exception is the live bait well runs on the engine batteries. So, I do have to keep an eye on at least one in the rear.

I wish I could tell you I set it up, but I didn't. I had it installed by a pro. I committed myself to rewire the boat this summer, so I guess it's time to learn.

Monnas Rock posted 05-24-2002 12:15 PM ET (US)     Profile for Monnas Rock  Send Email to Monnas Rock     

I would also be very appreciative of info on the 2/1 setup with an onboard charger, that hauptjm describes above. In the past, I have had several boats with hard wired onboard charging systems with so called "Float" chargers that still boiled your batteries. But, I'm told, the newest chargers can be, safely left plugged in all the time. Looks like there may be several interested parties. Could you post it?

Dick posted 05-24-2002 10:48 PM ET (US)     Profile for Dick  Send Email to Dick     

The Guest diagram is for outboards as well as inboards, with any brand of switch.
There is no real splitting or re-wiring to go to the alternator and starter. That split is done in the wiring harness of both.
The positive battery wire from the wiring harness attaches to the output connector on the switch, #1 goes to one battery positive, #2 goes to the other and that is all there is to it, outboard or inboard.

I admit that the Guest diagram shows, what looks like, you have to split to the alternator and starter, not true.

jimh posted 05-25-2002 01:51 PM ET (US)     Profile for jimh  Send Email to jimh     

I completely disagree. The diagrams shown by GUEST in the website (now a dead link) contain many suggested circuits that are entirely inappropriate for outboards.

I have revised my article about dual battery wiring arrangements to include the single engine/dual battery arrangement. Previously I had not mentioned this because it is really quite a simple circuit and I though it well understood.

I would strongly advise against trying to implement some of those exotic arrangments shown by GUEST (for use on inboards) with an outboard engine.

If I ever encountered an outboard engine which had been modified to incorporate separate alternator charging leads, sensing leads and starter motor wiring, I would run from it like the plague. See additional comments at the end of the article.

Dick posted 05-25-2002 08:27 PM ET (US)     Profile for Dick  Send Email to Dick     

It's a no brainer. The positive lead from the wiring harness that was attached to the positve battery terminal now goes to the output terminal on the switch. There is no exotic wiring required.

The wiring diagrams on Guest's web site and in their catalog may seem complicated, they are not if done by a marine technician.
In any of the applications there is no exotic wiring required unless you get into some of the inboards with inverters and chargers.

Ed Z posted 05-27-2002 11:29 AM ET (US)     Profile for Ed Z  Send Email to Ed Z     
I have a dual battery setup in my Nauset (one for electronics, other for engine)with one battery in each rear corner of the boat. I just use a marine grade battery isolator (really big diode) with no problem encountered over many years use. This setup keeps both batterys charged (from the engine charging curcuit) bith keeps them as separate output sources.
jimh posted 05-27-2002 10:04 PM ET (US)     Profile for jimh  Send Email to jimh     

It is hard to have a discussion about a wiring diagram that only you can see.

The ones I am talking about are shown by GUEST in the hyperlink above. They involve complex interconnection of isolators, alternator field sense wires, multiple switches, etc.

I have to stick to my opinion--none of that is applicable to outboard boats. I have published a wiring diagram in my article that is applicable.

If we are going to keep talking about this, you'll have to show us your wiring diagram.


Ready2Rip posted 05-28-2002 11:48 AM ET (US)     Profile for Ready2Rip  Send Email to Ready2Rip     
This is a timely thread for me - just had to spend an hour troubleshooting my battery cables so I could get back home yesterday. Turns out that one of my power cables that went into the battery switch had completely corroded apart. This will give me a good chance to map out my existing wiring diagram & compare it to the ones shown in this thread.

Good stuff!

Monnas Rock posted 05-29-2002 03:02 PM ET (US)     Profile for Monnas Rock  Send Email to Monnas Rock     
Thanks for the dual battery diagram. Hopefully I'll have a chance to use it soon.
mm2aganger posted 03-23-2009 05:44 PM ET (US)     Profile for mm2aganger  Send Email to mm2aganger     
[Revived this seven year old discussion to request that information be sent to him via email. The purpose of this website is to collect an organize information which can be easily browsed and acquired without email. We do not really encourage that information be exchanged via private email, as such private information exchanges are counter to the whole purpose of this website, a public exchange of information.--jimh]
cjmiller posted 03-24-2009 07:19 AM ET (US)     Profile for cjmiller  Send Email to cjmiller     
[Observed that a manufacturer offered advice for application specific to its specialized battery switch].


jimh posted 03-24-2009 08:13 AM ET (US)     Profile for jimh  Send Email to jimh     
Discussion of small boat electrical systems is now conducted in the discussion area SMALL BOAT ELECTRICAL. Please move further inquires about how to install a primary battery distribution system to the SMALL BOAT ELECTRICAL discussion.

[Thread closed in THE GAM.]

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