I've recently been told that installing my battery cables made for brighter headlights - something told me that his OEM cables were farther gone than originally thought...
I use 1 gage since it's good for about 250A for any run under 50' - and the longest we've got to look at it about 14' bumper to bumper.
As far as battery selection, I'm running Optima Red Tops backed up by 140A alternators - and I'll probably keep it that way until I get around to relocating the starting battery and adding the two deep cycles (blue top?) that I've got in mind - but I'm also planning on rerouting most of my lighting to go right to the secondary batteries, ditto the stereo and sub/amp, and some auxiliary two-way radios I haven't installed yet. I won't be using a solid-state isolator - they cost too much and I can do the job cheaper, better, and more reliably using a 100% DC solenoid.
Unless you are planning on running a lot of electrical stuff without your engine going at the time, a red top will serve nicely - the reserve capacity and Ah ratings are quite enough unless you are going to get silly. Save the deep-cycle idea for if/when you are going to run significant loads without the engine running and the alternator going - but it would be a good idea to upgrade your alternator and your mains cabling (and if you can't find a good rewind shop, mine is willing to do mail orders. I can give you contact information if you'd like - he's in San Jose, CA.)
For electrical loads - especially high-current electrical loads - there is no harm whatever in using a wire that is several sizes too large (and some good can come of it.) The larger cross-section presents a lower effective resistance, and therefore less drain in the circuit before the power gets to the consumer. Also, the fine strands of the welding cable that I use both make the cable more flexible (and therefore easier to handly) but also effective larger than a "battery" cable of the same composite gage (resulting in a higher ampacity.) Welding cable has about 150% the current-carrying capacity than a coarse-stranded battery cable of the same nominal gage.
I selected one gage cable as an effective compromise between shipping weight, cost, and overkill - you just don't need anything larger unles you're running several alternators, or a multi-kW generator under the hood. I honestly believe you're not going to use the full capacity of 1 gage wire with common equipment - including an average winch (and if you want to go larger than what's generally available, you're better off with fluid power or a PTO anyhow.)
If you have a lot of trouble rigging a headlight harness, let me know. I've been getting requests to see what I can do about costs on that little project, and if I feel like there are enough people interested, I'll do some digging and see what I can do. People seem to be happy with my battery cables (especially for the money you pay for them!) and I'm always willing to help fellow Jeepers save a few bucks...
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