rewiring a factory fuse to run off second battery

[ladorn45]

Hey Everyone,

So I installed a second battery in my car and have quick question. I want to hook up the rear trailer acc power wire to the second battery in stead of having it run off first factory one. The 2001 tahoe has a seprate fuse for this wire that is a 40 amp fuse. I was curious if I could just take a quick disconnetct clip (picture below) and put it in the half part of the fuse that leads to the back trailer hitch plug and then then run the wire to my alt battery with a new 40 amp fuse hooked up to it. Is there a reason why this is a bad idea or anything i should be worried about. I attached pics of the fuse box that i would be tapping into and the factury fuse i would be replacing.

 

[Sub]

Is there a reason why this is a bad idea or anything i should be worried about.

Yes, it is a bad idea, as it is wholly unnecessary. No need for fuse taps at all.

Just remove the fuse in the panel altogether. Attach an independently fused 8GA wire from your secondary battery directly to Stud 1, where the wire to the trailer harness is already attached. Done.

 

[ladorn45]

I think where on the same page you just did a better job explaning it. Basically take the quick disconnect connector and connect it to that pin run to bat and done. Also you think 10 awg wire would be enough and just use a 30 amp fuse.

 

[YukonXL04]

Is the 2nd battery connected to the main charging system or does it have separate charging? Cause if they are connected together it's not gonna matter which battery it's hooked to.

 

[ladorn45]

The batt is charged by the stock alt but there is a battery isolater on it so when the car is off the the two batts are seperate. You think i need a 8awg wire you dont think a 10 awg wire is good enough

Is the 2nd battery connected to the main charging system or does it have separate charging? Cause if they are connected together it's not gonna matter which battery it's hooked to.

 

[YukonXL04]

How far is the wire running?

And what are you powering with it?

 

[Sub]

I think where on the same page you just did a better job explaning it. Basically take the quick disconnect connector and connect it to that pin run to bat and done. Also you think 10 awg wire would be enough and just use a 30 amp fuse.

I wouldn't use a "quick disconnect connector." I would use a round eyelet terminal, just like GM does, on the charge wire that goes from your Auxiliary Battery to Stud 1. Fuse that wire as near as possible to your auxiliary battery.

If you have mounted the battery on the passenger side of the engine compartment, near the fire wall, where the second battery mounts in diesel versions of the GMT800, then you can buy a convenient Mega Fuse holder from GM that is designed to snap right into the second battery tray, in the open space under the cowl between the battery and the firewall. You can mount a 40 amp megafuse in that box, nice and protected, factory fit and finish.

Wire gauge is dependent on length of run and load. The load is assumed to be 40 amps, to replicate the trailer battery charge circuit that GM provides. If your run to Stud 1 is just 4 feet across the engine compartment, then know that GM only used 10 gauge... maybe even less. I bought all GM wiring to add my second battery, and that was the one wire I sent back to the dealer, as I felt I could do much better for less.

If you used 8 gauge, then that should be plenty. Just be careful to use a cross linked jacketed wire (denoted by letters like SXL, GXL, where the XL means cross linked insulation). The wire should be rated for 125 degrees Celsius. Most pvc jacketed wires are only rated for 80 degrees, which is not adequate to keep it from melting in the confines of the engine compartment.

 

[ccapehartusarmyINF.(ret)]

just curious why do you want yer trailer running off a second battery are you running some sort of refrigeration unit

 

[Granprixfan]

"just curious why do you want yer trailer running off a second battery are you running some sort of refrigeration"

I was wondering the same thing!


My best friend wants to put in a some accessories in the trailer to run independent or w/o generator (noise) he's an avid kayak fishermen
And his older brother retired got himself the top o Line RV got back in barn and ripped out the factory stereo and put in NOS German MBQuart top o line speakers and JL WL7 15" with some equally impressive amps and deep cells dedicated to this
all this before ever taking out for a test run
So ya
Since you're going through all the time and effort to do these stout electrical upgrades
I'm kinda curious what the end game is

 

[ladorn45]

I want to use the trailer hitch as an extra electrical access point. I took a 7 pin male trailer plug and wired it to have a poss and neg wire. The end goal is to be able to power what i want like a pump for the tires offroad lights or just simply a power inverter for tailgating