Dual batteries

[ThaEdge]

Strange. My dually has a solenoid and a long wire wrapped around the ABS pump and redundantly connected to something. It was defeated when the passenger battery was deleted. It makes me think GM didn't wire them as simply as has been described so far. I never have seen a schematic that shows this piece either. The solenoid is mounted to the fender back by the power distribution box. I too have had excellent luck with single batteries, but I do remember having less luck with batteries in general back when I lived in upper MI. One thing duals are good for is if the batteries are weak or freeze, you have a little extra to help you fire it off. Or if you have a hard starting POS.

That was a diy addition not factory or dealer add on.

 

[Supercharged111]

That was a diy addition not factory or dealer add on.

It has an 8 digit GM part number and is integrated into the factory harness.

 

[ThaEdge]

It has an 8 digit GM part number and is integrated into the factory harness.

Interesting... I'll have to do some more digging on that then. Can you send the part number? I'm intrigued now!

First guess is maybe somthing for an ambulance package or possibly for a camper. My truck has the camper package and doesn't seem to have anything like that.

 

[884x4310ci]

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Could not get them both in the same pic. But took 2 pics further back. So you can get the idea.
Don't mind the detention cord it's for a battery tender. Just have the rest in the hood instead of the ground.

 

[L31MaxExpress]

OK so this is somthing a know a little something about.

I haven't done this in my c3500 yet but I did a quite extensive aux power system on my Ram 2500 utility truck.

The batteries don't need to be the same if your running isolated systems as I am. So I have a starter battery that does just that. Meaning it ONLY goes to the starter. Everthing else runs on 2 large marine deep cycle batteries. For what you're doing I don't think you'll be needing 2 batteries. But if you're going to run dual start batteries then I would recomend you go buy 2 identical ones and start fresh. A week battery will shorten the life of the good one. If the old one goes bad it will make the new one go bad. And you'll be replacing both anyway. As far as wiring goes, make sure positive is connected to positive and negative to negative with heavy enough cables and you'll be fine. If I were doing it, just for simplicity sake, I would wire the new battery up by running 4ga wires to the old set up and connect them appropriately. Would take a few minutes.

^^^I have a deep cycle battery and a standard AGM battery in the 99 Tahoe on seperate alternators. My 8.1 came with a factory dual alternstor setup. I upgraded the alternators from the crappy stock 105 amps to junkyard 145a AD244s.

 

[Steven Petersen]

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Could not get them both in the same pic. But took 2 pics further back. So you can get the idea.
Don't mind the detention cord it's for a battery tender. Just have the rest in the hood instead of the ground.

Thanks. Did you have to eliminate or move the evap canister to make room for the driver side battery?

 

[884x4310ci]

I converted to carb. So I removed all the emissions stuff.
but I am pretty sure it all fits. Because it's stock parts.

 

[Nad_Yvalhosert]

Thanks. Did you have to eliminate or move the evap canister to make room for the driver side battery?

You do have to move the canister from the core support to the fender. I put mine at an angle, kinda under the driver battery. Just need to move the plastic line over and shorten it a little.

 

[El Tigre]

I relocated mine inside cabin reducing their exposure to temp extremes. Also moving them about seven feet to the rear takes some weight off an already heavy nose. Not to mention additional air circulation ,and open space.

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[df2x4]

^ Dual Odyssey 34/78s, you could probably start a space shuttle at -30F.