Ford's recommendations are recent... the Ford instructions posted above were republished just last year, in 2024.

THHN is building wire... buildings don't move like vehicles do.

In addition to moving down the road, vehicles also move via vibration. The strand count in THHN wire is significantly less for any given gauge. Coarser strands (thicker individual copper conductors) can fatigue when subjected to vibration.

THHN insulation is Thermoplastic High Heat Resistance Nylon Coating. The nylon coating is that clear film skin (for pulling), and the thermoplastic is PVC.

This PVC insulation in THHN is limited to 90°C, which is higher heat rated than the PVC insulation found in most micro-spools of automotive wire sold at the wax and oil auto parts chain stores, and Walmart, that is limited to only 80°C.

Yet both 80°C and 90°C fall significantly short of the 125°C that Ford recommends be used in engine bays and between frame rails under the chassis.

While we still await Pikachu's math on corrosion and stranding, at least the following math is self evident: 90°C does not equal 125°C.

As MDHunter pointed out, the literature on the welding cable upthread mentioned battery cable as a potential use.

I'd like to further point out that Ford's literature stated "use cross linked polyethylene SAE J1127 SGX or STX or equivalent," which does not preclude welding cable, as long as it is equivalent. 90°C does not equal 125°C.

In the original question in Post #1 of this thread, petrokiller asks, "when it comes to complete battery cable replacement, what is the top kit nowadays?"...

The "top kit" should be at least as good as what the OEM specified. And without keeping the OEM material specifications in mind, how can one determine if a purported top kit is even as good as as the stock kit? By the advertising? By the marketing? By the word of mouth from reviewers who may not have even considered the OEM specifications? Or by the OEM specifications directly? As long as the alternative cable is "equivalent" to what Ford recommends.

 

I should have said, I used the THHN on my Toy Hauler battery hookup.
not on the truck, it came with good cables, as is.

 

Top kit can have many different meanings and/or connotations. It could be top quality kit as you suggest. It could be top reviewed kit, top purchased kit, top dollar kit, top suggested kit...

The corect answer is subjective (or would it be relative?) to the person asking and the person answering. Everyone here has provided just as viable of an answer to his question as you have. You did suggest a kit didn't you?

 

No, I did not suggest a kit.

Rather, I suggested a principle.

The principle can be applied to evaluate any kit.

The examples I screenshotted were simply illustrations of wiring standards, to communicate the principle.

The company selected to illustrate the wire standard comparison was chosen based on MDHunter's comment about wire suppliers to NASA and the DOD, so I chose a supplier matching that particular pedigree, located in Georgia, the state of residence of the OP, in order to illustrate the principle.

 

I bought a complete set from Custom Battery Cables and couldn’t be happier. They use a 3/0 for the starter to the solenoid and from there to the battery. Then use a 2/0 everywhere else. Then when I upgraded to a 240 amp alternator, I ran 1/0 from the alternator to both batteries (pos and neg). Also installed a 300 amp fuse on the positive terminal of the battery to the alternator.
Basically a complete charging system upgrade. Only thing left is to get a pair of new Odyssey Extreme batteries when these cheap crap AAA batteries fail.
My 7.3 cranks strong, charges at 14.9vdc average and everything electrical including the engine runs healthier.
This is what I started with: https://custombatterycables.com/prod...2003-3-0-2300/

 

with the higher charging voltage, the existing batteries are going to live for a long time, yet.

 

On the home page of the CustomBatteryCables website linked by Rainmaker1 above, Vince, the owner of CustomBatteryCables, states that he uses STX and SGX (cross-linked jacketed) battery cables.

STX and SGX are what Ford requires for this application, as a guiding principle.

 

Y2K
So, if I found an electrical cable that meets SAE J1127 specs, a cable that is equal to or better than STX/SGX as far as oil and abrasion resistance, plus it must meet UL 1581 for flame retardation (which STX/SGX don't), would you be interested? OBTW is rated for 10 times the voltage of either STX or SGX.

Mike

 

Sorry @MDHunter , I've been offline for a week, and had a backlog of PM's to catch up with.

The 600V rating of cables isn't needed, when 60v rating is sufficient for 12v application.

High CURRENT, not high voltage, is why battery cable gauges are thicker. For the same electrical work performed, current is much higher at lower voltage, and current is much lower at higher voltage.

Example: My radial saw at 120v uses 15 amps of current, but when wired to 240v, only uses 7 amps of current. Another example: The 25,000 volt high tension wires at the top of power poles are rated for really high voltage, and yet are as skinny if not skinnier than the secondary 240v wiring output of the transformer.

So while I wouldn't turn down 600v rated wire for battery cables on that reason alone, I wouldn't favor 600v rated wire for that reason either. Voltage rating beyond 60v is simply not a factor in the decision for battery cables in an under hood engine compartment environment, in keeping with OEM vehicle specifications.

Oil and fuel resistance, as well as abrasion resistance, are excellent characteristics to look for in an automotive cable jacket... but what Ford, GM, Stellantis, Paccar, International, and other OEMs who speak to specifications for battery cables all require in common is the 125°C (257°F) temperature rating of the jacket. So that is the one trait that I would specifically seek, since the OEMs specifically mention it.

 

Even with my light OCD this is an easy one for me, legit Marine grade tinned copper or nothing, if you’re doing the job yourself.

 

that charging voltage might be a little high for AGM batteries? Alt in my truck will ramp up to 14.4 on a cold start…maybe will touch 14.5 for a brief time, then settle down to around 14.1 or 14.2 under normal temps. But I’ve seen it drop into the high 13s on a hot summer day working the engine hard to where it’s 130+ degrees under there.

 

I checked on the Mechman website and they state that their alternators are built to be compatible with AGM batteries. I’m having a pair of Walmart Everstart AGM batteries installed as I’m writing this post and confident that everything will work well together.

 

Would this tool work for crimping battery cables?
I have this tool I use at work to fix air hoses, but not sure it would crimp wires correctly.



Might need to buy an actual wire crimper like the one Sous posted have a couple of projects that need cables replaced.

 

I used to use one of those small anvils with a Vee shape and a 5 lb hammer.

decided to go Pro and bought this

 

Not sure how that works, bottom line is that you need a crimper that compresses the soft copper strands and connector into a solid mass within the connector, where air and water can't get in. Best way to check is do a test crimp and then saw it in half, if you see strands it's not good enough, needs to look like a solid copper mass.

MY crimper is a little bit more than a diy would want to invest, but makes beautiful crimps

​​
https://www.amazon.com/TE-CONNECTIVITY-AMP-600850-CRIMPING/dp/B011OLRJYS

Now, truth in lending, the crimpers were purchased for a job where the crimps / connections had to be inspected and certified. I got to keep the crimpers 😁