you must be vastly confused on the way the automotive charging system works, the battery has to get its power from somewhere, that would be the alternator, the factory 8 ga wire isnt big enough to support much more than the factory electrical system, this is why we upgrade the wire going from the alternator to battery, block to frame and the battery to frame (big three).I apologize for not making abundantly clear in reply #13 that it was a continuation of reply #11, and for the confusion over it's wording. Reply #13 should start:
"I forgot to mention in reply #11 and the following is in reference to it"
I would have preferred being able to edit directly into reply #11 versus a separate reply, while also using the later improved wording.
I suspect that in reply #16 you are refering to "over fusing" as well as the use of a circuit breaker, in reply #13. If so by "over fusing" I refer to using a fuse of higher amperage rating then is recommended. And breakers often slower to react can allow surges while still limiting the average current, thus better then "over fusing" and similar to using a slow blow fuse. I would however agree, reply #16, more protection where needed is better. With that the current ratings in reply #11, for those that would like to know some recommended values, are from a reference which I use.
My only real contradiction of the original post is: There is no need upgrade the stock small wiring when it is just as easy to go to the source (the battery) or at least to the where the heavy gauge wires (cables) that can handle the current end, when either method will generally do.
If however you are upgrading to a 200amp alternator then go ahead and put in 0000 gauge wire or double up on 1 gauge, it should only help. And if you prefer to change "your big three wiring" as per the original post and it's reference, you might also consider same for frame (or engine block or battery - ) to cab body, if intending to use it for a negative connection (grounding point) for everything.
Again I apologize, for any confusion over my input. Would you please point that thing somewhere else.
8 ga wire is only rated for 40 amps, even the factory alternator puts out 90 so they were going cheap from the factory, so if you upgrade to a higher output alternator you will need even heavier wire.
also 0000 wire is very few and far between in mobile installations and is for the most part impractical to most members on this forum. 0 ga or at most 2/0 is the largest nearly anyone would need.