Welding cable works great for this application. It too, is high strand count copper.
While I totally understand that not everyone is capable (or willing) to make their own cables, and these kits are just the right kind of solution for them ... $120+ bucks is a lot of money for three lengths of cable w/terminations, a few zip ties, a little bit of heat shrink tubing, and an alcohol swab.
As far as the trick cable in those kits, it all comes down to pounds-per-foot of copper. All that high strand count provides is more copper per foot in a smaller diameter cable, and increased flexibility. If one wishes to DIY this, as I mentioned, welding cable is an excellent substitute. There's actually only about $15 bucks worth of components in those cable kits. I can offer assistance for making a solid crimp on the copper eyelets if anyone wants to look into the DIY solution. Send me a private message if you need help with how to crimp those copper eyelets. I'd be happy to help.
Another thing that may help is stuff known as "gas tight paste" which is impregnated with metal crystals (zinc). The metal crystals cut through the mico-thin layer of oxidation on the eyelets and the terminal posts that forms in less than a few milliseconds after the surface(s) are machined/sanded/brushed/whatever clean. The crystals cut through that layer of oxidation, then the "gas tight" substrate seals the connection from air/oxygen to prevent oxidation from creating resistance (which increases load on the battery, and decreases voltage to the starter). When voltage goes down, current goes up. And when that happens, windings on the starter's armature and stator are carrying more current than they were designed to, leading to component failure.
I build modular synthesizers, I hand make bus bars and power cables in the custom power distribution system. And as you may have guessed, I use gas tight paste on all of the DC connections and terminations. Modular synths are highly sensitive to voltage drop and voltage differences from one end of the distribution to the power supply. Using the methods I've described reduces those issues to near null.
So even if your starter is working ok for now, uprating to cables with more copper per foot is a solid preventive measure.
Originally Posted by BelgianDuc900SS
If you're starter motor is broken, bigger cables will of course not fix that but they might help to prevent problems in the future with your new starter motor.
That's a fact, Jack!
"Why is there never enough time to do it right, but always enough time to do it over?"