Adding a Dual Battery

[davester]

maybe describe when/how you want use the 2nd battery, and when/how you want the battery to be charged?

[jpinoy]

So, as the parts came in, they sat around for a while(ok, a good while) finally got around to installing my dual setup. 

I picked up the Keyline Isolator 300amp(for future, friends trying to talk me into Overlanding.. haha) and AGM H6(Costco). The design for the battery terminal on the back of the isolator could use some redesign, or make it like their 140amp isolators.  If you buy their kit, you get the right terminals to fit from the looks of it. I bought some copper tubing and made my own lugs to fit correctly on the back terminals.. 

I used some red wire-loom for positive cables, but, I might switch it out with black. I picked up MTA 0300839 fuse block to use on it. I did pick up a 4 Relay/12 Fuse holder, just need to figure where to mount it, most likely in the corner next to the aux battery on that corner bracket. I'm going to re-wire it using the more flexible silicon wires. 

I did go the sensor route with the negative cable(used 2AWG). My old man gave me 1AWG red/black welding cable, so used the 1AWG for the positive. I connected some leads to the aux battery so I'm able to plug it into a maintainer, comes out by the bottom front grill. 

I left some of slack on the main cables if I need to move/route them. I used 2 fuse, between the isolator and main/aux battery. I ordered some wire loom mounting clips to clean up that side wiring/cabling. Most likely move the fuse onto the firewall for a cleaner look. 

 

 

Don't mind that cable hanging down, it's going to get re-routed, it's for the LED strips.

 

 

 

 

 

[eurobound]

Some pics from factory 2nd battery installation. Works fine so far other than first 125 amp fuse provided was actually blown. Replaced it and it's worked solid for over a year now.

 

Buying the factory stuff was quite nice as it was totally plug and play with not much fuss. Wires fit perfectly and connectors to hold wires just snapped into place. Highly recommend going this route.

 

I also replaced both batteries at that time with AGM and so far no issues. 

[avin]

Hi. 
looks great. What are the other smaller wires for running from the pos and neg? Thanks

[eurobound]

Good question. I attached a Victron Battery Sense to monitor the batteries.

[BackRoadZ1]

On 3/17/2024 at 11:13 AM, eurobound said:

Some pics from factory 2nd battery installation. Works fine so far other than first 125 amp fuse provided was actually blown. Replaced it and it's worked solid for over a year now.

 

Buying the factory stuff was quite nice as it was totally plug and play with not much fuss. Wires fit perfectly and connectors to hold wires just snapped into place. Highly recommend going this route.

 

I also replaced both batteries at that time with AGM and so far no issues. 

Do you have a parts list with part numbers for your kit?

[GraphiteSilveradoZ71]

On 3/17/2024 at 11:13 AM, eurobound said:

Some pics from factory 2nd battery installation. Works fine so far other than first 125 amp fuse provided was actually blown. Replaced it and it's worked solid for over a year now.

 

Buying the factory stuff was quite nice as it was totally plug and play with not much fuss. Wires fit perfectly and connectors to hold wires just snapped into place. Highly recommend going this route.

 

I also replaced both batteries at that time with AGM and so far no issues. 

I came across this feed and something similar in another group. I’m looking to do the same if not similar on my 5.3L 1500.

Is this on a 5.3L/6.2L 1500 truck or 6.0L 2500/3500?

the black connector coming off of the grey relay, what does that connector go to? I’ve tried looking up the wiring diagram and have had no luck.

[eurobound]

On 12/24/2025 at 6:05 PM, GraphiteSilveradoZ71 said:

I came across this feed and something similar in another group. I’m looking to do the same if not similar on my 5.3L 1500.

Is this on a 5.3L/6.2L 1500 truck or 6.0L 2500/3500?

the black connector coming off of the grey relay, what does that connector go to? I’ve tried looking up the wiring diagram and have had no luck.

It's been a while since I did this upgrade and don't remember much. I do know though that there were unused OEM connectors in the engine bay and this was just plug and play. Not sure if the extra pics will help. Good luck!

 

Edit: as per my signature, it's a 6.0L gas 3500HD

 

FWIW, It's been working well ever since I did it.

 

I personally would not mess around with aftermarket if I was given the chance to do it again unless for some reason I needed to upgrade the wiring. I have a nice aftermarket sound system installed with 1800 watts (2 Class A/B 900 watt amps at 4 ohm (6 x 150 per channel)) as well but as anyone will tell you the actual amp capacity needed to support even loud listening levels is well below the threshold of the alternator and wiring in this truck. This would be true except for SPL installs - that's a whole other animal. Just thought I'd throw that in there for anyone thinking they can't go with this OEM option as it won't be good enough for their car stereo system. 

Edited December 26, 2025 by eurobound