need wiring help

JHensel · Aug 31, 2009

Hello, I am adding an extra battery to my van and I need some help.

1. I want to isolate the second battery so it can't drain the main battery. I have no idea how to do this. Should I buy an isolator and try to do it myself, or should I have someone do it for me?

2. I am adding some lights, the usual white dome RV style, they have two wires coming out, one white, and one black. Should I make sure that the wires coming from the battery are the same size as the wires coming out of the light? Also I want to add an inline fuse and I am not sure if it matters what size the fuse is.

3. I am adding a DC outlet as well. There are no instructions with the outlet. The outlet is the simple faceplate and barrel. There is a connector on the outside of the barrel and a threaded stud on the end of the barrel. I am assuming that the treaded connection is the positive and the outside is the NEG. The NEG has a small gauge white wire connected to. My questions are, what gauge wire should I connect it to the battery with. Can I discard the small white wire and use a larger wire? Also what size inline fuse should I use.

Any advice would be great.

Thanks

J

DonTom · Aug 31, 2009

Welcome to the forum!

It would be helpful to mention what type of vehicle you're doing this work to. Below is some general instructions for adding a house battery when you only have a chassis battery.

JHensel said:
Hello, I am adding an extra battery to my van and I need some help.

1. I want to isolate the second battery so it can't drain the main battery. I have no idea how to do this. Should I buy an isolator and try to do it myself, or should I have someone do it for me?

First, disconnect your alternator output. The alternator output goes to the center of the isolator and the other two posts of the isolator go to one battery each. This keeps both batteries charged and isolated from each other. Then just add the 12 volt stuff you want to add to the new battery. If you understand this much do it yourself. If you don't, let somebody else do it for you.

2. I am adding some lights, the usual white dome RV style, they have two wires coming out, one white, and one black. Should I make sure that the wires coming from the battery are the same size as the wires coming out of the light? Also I want to add an inline fuse and I am not sure if it matters what size the fuse is.

The more lights it runs, and the more current each draws, the thicker the wires should be that go to the battery. Too thin can cause a problem, too thick cannot. You can add the current ratings of all the lights and other 12 volt stuff you wish to run and then we can give you an idea of what gauge wire to use.

There is a connector on the outside of the barrel and a threaded stud on the end of the barrel. I am assuming that the treaded connection is the positive and the outside is the NEG.

Yes, that is correct.

Can I discard the small white wire and use a larger wire?

Yes.

Also what size inline fuse should I use.

It might already contain a fuse. See if you can unscrew the center pin or unscrew the entire unit to see if there's a fuse already inside. If not, you have to decide the maximum current you will draw from the outlet and have a fuse rating just above that.

-Don- SF, CA

Bob Flight · Aug 31, 2009

The battery isolator comes in 2 popular types. This wiring link shows both types and sample schematics of how they are wired.

The DC receptacle usually has a limit of 15 amps. I would apply an in-line fuse no bigger than that. Crimp on connectors are a good method to connect the wires.

The lights are following residential wiring color codes. The black is the positive lead and the white is the ground. It is important to follow that so that the positive connections are protected from accidental shorting to surrounding parts, as intended by design. Using a small volt meter will help confirm the polarity of your connections. The small lights are low current draw items. Depending on the wattage of the bulb, a 3 or 5 amp fuse is all that is needed. Our library has a chart of bulb size, wattage, and other factors, here. We also have a Wire Size calculator program that can be install, also in our library, wire calculator .

Hope these help.

need wiring help

JHensel

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DonTom

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Bob Flight

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