Which battery should I run in my 04 Chevy 2500HD with 3100 watts?

[SkwurlyFab 10+ year member]

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[tommyk90 5,000+ posts]

Thanks for the pics. Yep, as far as I can tell the batts don't look isolated, however it looks like there are stock wires running to that 2nd battery which leads me to believe that the truck had the wiring for a 2nd battery stock but not the battery itself.

Now it's hard to say if they are actually separate or not, but I don't think they would be separate from the factory as that defeats the purpose of having two batteries from the factory since they would be used for starting purposes. Only way to know for sure is to test the voltage and see what you get.

As for the wiring itself, one definite upgrade I would do is running 1/0 from the front batt/alt to the 2nd battery since your system relies heavily on those connections.

Then do the big 3 as well, which is pretty easy to do on your truck.

Here's a pic of mine done (minus the engine to frame ground, gonna do that eventually):

 

[SkwurlyFab 10+ year member]

Yeah that 2nd battery in the back has the stock wire loom on a wire coming off it that goes to a little plastic box behind the battery. i couldn't get a photo of it really since it was so dark behind there but maybe it's an isolator? I dunno I even hit up the previous owner of the truck and he said the guy he bought it off of had a big system in the truck and added the 2nd battery so there may be an isolator in there.

the 2 batteries do read different levels when the truck is off so wouldn't that mean there's something keeping them from being connected in parallel?

 

[tommyk90 5,000+ posts]

Yeah that 2nd battery in the back has the stock wire loom on a wire coming off it that goes to a little plastic box behind the battery. i couldn't get a photo of it really since it was so dark behind there but maybe it's an isolator? I dunno I even hit up the previous owner of the truck and he said the guy he bought it off of had a big system in the truck and added the 2nd battery so there may be an isolator in there.
the 2 batteries do read different levels when the truck is off so wouldn't that mean there's something keeping them from being connected in parallel?

How different are we talking? Few tenths? .5 or more? Some of that might just be resistance in the wire/connections.

What are both the batteries resting at?

If it's a good difference, then yes it seems like they may be isolated with the car off, however that isn't of importance to you since they will be connected when the truck is running. Regardless, you need to replace that bad yellowtop with the D3400 you got and upgrade all of your wiring. This will do nothing but help your setup.

 

[SkwurlyFab 10+ year member]

So I replaced the faulty Yellowtop in the back of the engine bay with and XS Power D3400. Power is better but still cuts out at high volume on certain bass heavy tracks. So the electrical system is not up to part quite yet but it's def better than it was.

When I took out the bad Yellowtop I noticed a funny little fuse box behind the battery with wire leads coming off each side. One side connected to the positive terminal of the 2nd battery and it appears to be OEM equipment. The other end plugs into a plug type thing in the firewall and goes inside the truck somewhere. Could this be an isolator that was included from the factory?

 

[SkwurlyFab 10+ year member]

anybody got any ideas if that's an isolator or not in the last set of pics?

 

[aviator08 10+ year member]

idk on the pics, but I was able to fit a kinetik hc200 in the front, but didnt like the kinetik and got d2700 instead (currently got a d3400). Also for the aux batt did you need a tray or did it just mount right on?