Battery Isolator Wiring Question...

parallon

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Hello all. I know there are many posts pertaining to this topic, but don't think I found what I am looking for. I have a Lowe 21' pontoon boat with a 2006 Mercury 60hp Big Foot motor. I want to add an aditional battery, so I bought an isolator. I remember using one on my car once, and connected the alternator to the center post, and 1 battery to each post, and the starter came off the first battery. Well, when I looked at this Mercury a little closer, it looks as if the same cable is used to charge the battery and to start the motor. Is this correct? There are only 2 cables, the positive and the ground, coming out of the engine. If so, how would I get this system to use a 3 post isolator?

Thank you for your time,

Mike
 

Timestep

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Re: Battery Isolator Wiring Question...

Hi Mike

I have one on my 60efi. Engine lead to middle terminal, each battery on left and right, connect all black wires together. One battery has absolutely nothing connected to it, the other has the bilge pump.

This allows me to start on either battery and then switch to both, to charge both.

It does need to be make-before-break as the voltage regulator is happier if it has a load. But most two way battery switches are.

Regards

Dave
 

Chris1956

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Re: Battery Isolator Wiring Question...

Mike, Dave was discussing a battery switch.

If you want to install a battery isolator, you need to find the charging wire on the outboard and extend it to the bilge, where you can connect it to the isolator. Then you need cables to each battery. If you don't have a battery switch, you will need to choose one battery as your starting battery.
 

parallon

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Re: Battery Isolator Wiring Question...

Chris1956, thank you for your input. I understand the basic concept, I just don't understand how to separate the charging cable from the starter cable. They seem to be the same one. Do I need to separate them within the engine where the alternator and starter cable come together? From what I could tell, the hot lead from the battery went straight to the starter solenoid, and the alternator went to the DC Rectifier and then to the same post on the starter solenoid. The rest of the harness that goes to the cabin seems to come off the same post of the solenoid as the previous 2 cables. I am assuming I can just leave all wires currently connected to the solenoid, and run that to one of the battery posts on the isolator, and then and just disconnect the wire coming from the DC Rectifier and run it to the center post of the isolator? Does that make sense?

Thanks,

Mike
 

Silvertip

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Re: Battery Isolator Wiring Question...

There IS NO separation. You are correct that the large battery cable carries current both ways. It charges when the engine is running (current to the battery) and when starting, current goes from the battery. If you look at the starter solenoid, you will see the large battery cable (the one from the battery) is connected to one of the large terminals on the solenoid. On that same terminal is another smaller wire which is the charging line.
 

parallon

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Re: Battery Isolator Wiring Question...

Silvertip, that is EXACTLY what it looks like. So, which wire do I run to the center post of the isolator? Which one to the positive post on the primary battery?

Sorry for all the questions, just don't want to fry anything.

Thanks,

Mike
 

Timestep

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Re: Battery Isolator Wiring Question...

Hi Mike

See post #2

Dave
 

parallon

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Re: Battery Isolator Wiring Question...

Thank you Dave, but I have not gone with a switch. I may in the future, but for now just want to get this isolator figured out.

Thanks,

Mike
 

Timestep

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Re: Battery Isolator Wiring Question...

The "switch" is 4 position. Off (isoloation), left, right, and both. What did you want to do?

Dave
 

parallon

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Re: Battery Isolator Wiring Question...

Oh, I see what you are getting at. The isolator I have has three posts with no switch. Battery A and Battery B and the charging post. Solid state. Just need to figure out how to separate the alternator and the starter in the motor since they run on the same cable. Would i remove all wires from the solenoid except the one going to the battery and amp meter (for charging) and run that to the center post, and tie the remaining together and connect to primary battery positive post? What Silvertip explained above is the current configuration.

Hope that makes sense.

Thanks,

Mike
 

Timestep

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Re: Battery Isolator Wiring Question...

Hi Mike

That isn't an isolator as such, it is a pair of "blocking diodes". You don't separate the wires, you leave it as it is with either solution

Regards

Dave
 

Chris1956

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Re: Battery Isolator Wiring Question...

Dave, Mike is discussing a "Battery Isolator". You are correct that it is simply a pair of heavy duty diodes in a heat sink, but it is used to automatically charge two or more batteries. You might look one up in a marine catalog to see what he means.

Mike, Have you considered a "Battery Combiner". They are a bit better technology.
 

parallon

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Re: Battery Isolator Wiring Question...

Chris1956,

That sounds totally possible. I looked one up and refered to all the diagrams, but they all show the use of a switch. If I didn't want to use a switch, could I just run the Alt/Starter cable from the motor to the primary battery and run the combiner between the positive posts of the batteries. That way when charging, both batteries will charge, and when voltage of one of the batteries drops, the relay will open separating the batteries? I realize that I won't have the option of using either or both batteries, for starting.

Thanks,

Mike
Mike
 

Timestep

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Re: Battery Isolator Wiring Question...

Hi Chris, thanks for that. I don't need to look anything up, as you say "You are correct"

I think we need to know what functionality Mike is looking for?

Dave
 

parallon

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Re: Battery Isolator Wiring Question...

Chris1956, just to let you know, that is totally what I am looking for. I talked to a rep for one of the companies, and they verified my situation. Timestamp, just wanted to charge 2 batteries without using a switch. The only issue with using the "isolator" that I have is that the starter and alternator used the same wire to the battery. At the isolator that I have, I would need to split that. This solution keeps me from having to do that.

Thanks,

Mike
 

Chris1956

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Re: Battery Isolator Wiring Question...

Mike, I think the isolator and the combiner have exactly the same wiring issue for an outboard. You will need to extend the charging wire from the voltage regulator out of the outboard cowling and connect it to the isolator or combiner.

The starter cables get wired to the output of the isolator or the battery post, on the battery you want to use for starting. Alternatively, the starter cable goes on the starting battery when using the combiner.
 

Faztbullet

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Re: Battery Isolator Wiring Question...

The easiest way to do this without modifiying wires to engine/harness, adding ground straps is to get a "charge on the run' charger. I sell and install a lot of these... Install in 20 minutes or less.....
http://www.dualpro.com/store/items/10/49/
 

swamp-fox

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Re: Battery Isolator Wiring Question...

Fazt that is sweet. So all you have to do is connect that to the batteries and it charges both while it runs? Thanks
 

parallon

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Re: Battery Isolator Wiring Question...

Not to mention cheaper than the "DualPro" mentioned above. :)
 
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