Battery Cables and Ground Upgrades

[SquareFace]

YJ Friends,

As I am mending from surgery and off of work, I decided to take a deep dive into our YJ’s electrical system prior to replacing my battery and cables/grounds.

I referenced our FSM for this foundation: (see attached diagram)

– 4 ga battery → starter

– 6 ga battery → PDC

– 4 ga battery → engine block

– 8 ga battery → firewall

– braided head → firewall strap (and hood strap on some)


Then used AI assistance from Chat GPT and Gemini, resulting in this as a possible improvement:

To upgrade your Jeep YJ's electrical system based on your specific factory list, we will move from a "decentralized" stock setup to a "high-capacity hub" setup. This plan prioritizes maximum cranking power and clean grounding for your electronics.


The "Big 7" Modification Blueprint


1. Positive Side (+) Upgrades


• Battery → Starter (Currently 4 ga): * Action: Replace with 2 AWG.

• Reason: The starter is the highest-current component; 2 AWG reduces resistance for faster, more reliable cranking.


• Battery → PDC (Currently 6 ga): * Action: Replace with 4 AWG.

• Reason: This feeds your entire fuse box; 4 AWG ensures consistent voltage to your lights and sensors.


2. Negative Side (–) "Hub" Upgrades


• Battery → Engine Block (Currently 4 ga): * Action: Replace with 2 AWG.

• Reason: This is the primary return path for the starter. Use the block stud near the oil dipstick.


• Battery → Firewall (Currently 8 ga): * Action: Delete / Redirect.

• Reason: Rather than running a thin wire from the battery to the firewall, you will now ground the firewall to your new Frame Hub using 4 AWG. This prevents "ground loops" and provides a much stronger body ground.


• Engine → Frame (New Connection):

• Action: Add 4 AWG cable.

• Reason: This completes the "Big 3" circuit, bonding the drivetrain to the chassis.


• Frame → Firewall (New "Hub" Connection):

• Action: Add 4 AWG cable.

• Reason: This replaces your old 8 ga battery-to-firewall wire with a heavy-duty bridge from the frame.


• Braided Head → Firewall Strap: * Action: Leave Intact (or replace with 4 AWG).

• Reason: This strap is primarily for radio noise (EMI) suppression. It is good redundancy, so keep it or upgrade it for extra cleanliness.


Final Grounding "Stack" Order


To ensure your mechanic does this correctly, use this "Star Ground" logic at the Frame Hub (on the passenger-side rail):

1. Sanded Bare Metal Frame (Apply Noalox).

2. 4 AWG Lug (Coming from the Firewall).

3. 4 AWG Lug (Coming from the Engine Block).

4. Hardware: Zinc-plated Flat Washer \rightarrow Split Lock Washer \rightarrow Grade 8 Bolt.

By following this, you have upgraded every factory gauge by at least one size, added critical frame bonding, and eliminated the weak 8-gauge firewall bottleneck.

This is a big read, but if you have time, take a look and let me know what you think.

Thanks in advance!

 

[DogFoxInd]

You'd need a kit like this:

Battery cable kit

 

[dieselearl]

good job, thanks for information.

 

[MwEgg]

YJ Friends,

As I am mending from surgery and off of work, I decided to take a deep dive into our YJ’s electrical system prior to replacing my battery and cables/grounds.

I referenced our FSM for this foundation: (see attached diagram)

– 4 ga battery → starter

– 6 ga battery → PDC

– 4 ga battery → engine block

– 8 ga battery → firewall

– braided head → firewall strap (and hood strap on some)


Then used AI assistance from Chat GPT and Gemini, resulting in this as a possible improvement:

To upgrade your Jeep YJ's electrical system based on your specific factory list, we will move from a "decentralized" stock setup to a "high-capacity hub" setup. This plan prioritizes maximum cranking power and clean grounding for your electronics.


The "Big 7" Modification Blueprint


1. Positive Side (+) Upgrades


• Battery → Starter (Currently 4 ga): * Action: Replace with 2 AWG.

• Reason: The starter is the highest-current component; 2 AWG reduces resistance for faster, more reliable cranking.


• Battery → PDC (Currently 6 ga): * Action: Replace with 4 AWG.

• Reason: This feeds your entire fuse box; 4 AWG ensures consistent voltage to your lights and sensors.


2. Negative Side (–) "Hub" Upgrades


• Battery → Engine Block (Currently 4 ga): * Action: Replace with 2 AWG.

• Reason: This is the primary return path for the starter. Use the block stud near the oil dipstick.


• Battery → Firewall (Currently 8 ga): * Action: Delete / Redirect.

• Reason: Rather than running a thin wire from the battery to the firewall, you will now ground the firewall to your new Frame Hub using 4 AWG. This prevents "ground loops" and provides a much stronger body ground.


• Engine → Frame (New Connection):

• Action: Add 4 AWG cable.

• Reason: This completes the "Big 3" circuit, bonding the drivetrain to the chassis.


• Frame → Firewall (New "Hub" Connection):

• Action: Add 4 AWG cable.

• Reason: This replaces your old 8 ga battery-to-firewall wire with a heavy-duty bridge from the frame.


• Braided Head → Firewall Strap: * Action: Leave Intact (or replace with 4 AWG).

• Reason: This strap is primarily for radio noise (EMI) suppression. It is good redundancy, so keep it or upgrade it for extra cleanliness.


Final Grounding "Stack" Order


To ensure your mechanic does this correctly, use this "Star Ground" logic at the Frame Hub (on the passenger-side rail):

1. Sanded Bare Metal Frame (Apply Noalox).

2. 4 AWG Lug (Coming from the Firewall).

3. 4 AWG Lug (Coming from the Engine Block).

4. Hardware: Zinc-plated Flat Washer \rightarrow Split Lock Washer \rightarrow Grade 8 Bolt.

By following this, you have upgraded every factory gauge by at least one size, added critical frame bonding, and eliminated the weak 8-gauge firewall bottleneck.

This is a big read, but if you have time, take a look and let me know what you think.

Thanks in advance!

View attachment 124439

Very nice analysis! A guy, jfleland, on Jeepforums recommended jeepcables.com and I just received their kit. Went with the stock 4guage kit. Nice stuff. The corrosion, damage and voltage drops around the jeep makes this work a no brainer. Your principles make sense and will add to kit. Two gauge to starter I don’t think is really necessary but what the heck. Drove and worked on big starters and batteries in over the road trucks so know big and clean are most important. I can now get back to inside work.

 

[MwEgg]

Very nice analysis! A guy, jfleland, on Jeepforums recommended jeepcables.com and I just received their kit. Went with the stock 4guage kit. Nice stuff. The corrosion, damage and voltage drops around the jeep makes this work a no brainer. Your principles make sense and will add to kit. Two gauge to starter I don’t think is really necessary but what the heck. Drove and worked on big starters and batteries in over the road trucks so know big and clean are most important. I can now get back to inside work.

View attachment 124510

Most important, comes with TWO stickers!

 

[SquareFace]

After discussing this further with @machoheadgames —who originally helped ground (no pun intended) my understanding of the FSM layout—and talking through the alternator and grounding paths, I’ve decided not to pursue the frame-mounted grounding hub approach.

Here’s why:

• The YJ frame is 30+ years old. Even if it looks rust-free externally, internal corrosion and inconsistent conductivity are unknowns.
• Creating a new grounding hub introduces a longer ground path rather than a shorter one.
• The factory system already grounds the starter return directly to the engine block, which is optimal for cranking current.
• Adding complexity where it isn’t clearly needed didn’t sit right with me, especially for a mostly stock electrical system.

So instead, I’m sticking with the factory grounding architecture, refreshed with new cables and clean connections.

My current plan:

• Replace battery cables with a quality Jeep-specific 4 ga cable set from Jeepcables.com
• Retain factory routing and grounding points
• Replace the braided engine-to-firewall ground strap with a new one
• Focus on clean metal, good hardware, and proper torque rather than reinventing the system

I’m going to run 4 ga for all battery and ground cables using the Jeep Cables Big 7 kit. The main reason is simplicity and quality.

Finding mixed-gauge replacements (4 / 6 / 8 ga) that are equal or better than OEM quality is honestly more work than it’s worth. The Jeep Cables kit is well-made, properly crimped, and sized correctly at all terminations, and using one gauge across the board keeps the install clean and consistent.

I don’t see any downside to upsizing the factory 6 ga and 8 ga runs to 4 ga:

• Lower resistance is never a problem in low-voltage automotive systems
• The PDC and firewall grounds are not sensitive to larger conductor size
• No risk to fuses, modules, or alternator regulation
• Shorter voltage drop during cranking and accessory loads
• Easier future troubleshooting with uniform cabling

Importantly, this does not change the factory grounding architecture—only the conductor size and cable quality.

So the final layout will remain factory-correct, just upgraded:

• 4 ga: Battery → Starter
• 4 ga: Battery → PDC (upsized from 6 ga)
• 4 ga: Battery → Engine block
• 4 ga: Battery → Firewall (upsized from 8 ga)
• New braided engine/head → firewall ground strap

This felt like the best balance of OEM logic + modern materials + install simplicity, without introducing unnecessary complexity or frame-based grounding variables.

Appreciate all the input

 

[SquareFace]

Very nice analysis! A guy, jfleland, on Jeepforums recommended jeepcables.com and I just received their kit. Went with the stock 4guage kit. Nice stuff. The corrosion, damage and voltage drops around the jeep makes this work a no brainer. Your principles make sense and will add to kit. Two gauge to starter I don’t think is really necessary but what the heck. Drove and worked on big starters and batteries in over the road trucks so know big and clean are most important. I can now get back to inside work.

View attachment 124510

Awesome! Please let me know how it goes! Are you installing the external fuse?
What about the wire to the alternator? Messing with that plastic isolator for the cable to fit made me hesitant.

 

[Y-YJ]

So I looked into the Jeep cables site.
I have some questions that others here Maybe able to explain.
Are there any advantages for a Heavier Gage wire than #4
I see that you @SquareFace choose 4G.
What are the advantages for the other 2 options they offer.
2GA - 1/0GA

 

[SquareFace]

From what I gathered, the thicker gauges add no benefit for people running relatively stock setups, as our electric demands aren’t that robust.

Plus thicker cables are harder to maneuver.

I’ve also read about people with the 2Ga Jeep Cables that have been quite happy with them.

I’m just leaning towards thinner, more maneuverable cables so I can tuck them away nice and clean. Or at least as clean as possible since some are still thicker than stock.

 

[Y-YJ]

I would like to see some photos when you're finished with your install. I believe that most of my cables are still in good condition but I'm sure they probably have some oxidization due to being 30+ years old. The only thing my YJ has going for it, is that it has always been garaged and only driven in the summer months.
What tires do you have that are in your avatar? I like the looks of them.

 

[Flyer58]

I would like to see some photos when you're finished with your install. I believe that most of my cables are still in good condition but I'm sure they probably have some oxidization due to being 30+ years old. The only thing my YJ has going for it, is that it has always been garaged and only driven in the summer months.
What tires do you have that are in your avatar? I like the looks of them.

I cut open the cables on my tractor which looked great but only had one wire strand in the white corrosion powder hiding inside the insulation.

I like the single big fuse vice the two smaller automotive fuses. I only have one LED light bar up front so I'll go for the 4 gauge size.

 

[SquareFace]

I would like to see some photos when you're finished with your install. I believe that most of my cables are still in good condition but I'm sure they probably have some oxidization due to being 30+ years old. The only thing my YJ has going for it, is that it has always been garaged and only driven in the summer months.
What tires do you have that are in your avatar? I like the looks of them.

Thanks! Those are 31inch x 10.5 inch mud terrain tires. I forget the name, but they aren’t anything special. The Jeep is still getting re-regeared so I can’t run out and check.

A nice pristine YJ is where it’s at! I had to have mine shipped from California to make sure I didn’t have too much rust to deal with. Problem is it came with a terrible aftermarket suspension and 1 functioning speaker instead lol.

I will send you some pics of when it’s done. Hopefully others do the same.

Attaching some side shots of my tires. Not sure why the pics are rotated. Sorry about that.

 

[Y-YJ]

Thanks I added your photos to mine so I could rotate them and check it out.

I had no idea that so many others where working on correcting and wanting to bring there YJ's close to Factory until I started looking around this forum today. I acquired my YJ this fall as a Winter Beater and bought the 16"wheels with 36" Buchshots on them so, I didn't have to use any of my other trucks in the salt and calcium while I remained home for this winter. It wasn't until I started rolling around beneath it in the Garage and getting ready to spray Waxwool on the hole thing that I came to realize what I had.
Since then I've put it in the barn until late spring / summer and have choosen not to run it this winter.
The Jeep was my fathers for 30 year and had never been driven in the winter, was always kept garaged until last spring when he started using that garage bay for another toy.
Just recently I mentioned to him that I replaced the headlights due to one not working, and his response was that he would have never known that because he had never driven it after dark.