Oh great, I thought I was reviewing Ohm's law reading your text, then I get to your visual, and I forgot what the heck we were talking about here.
That 77 one ton flat bed with a 454 and 4 speed out in the yard is the prime example as to why #4 battery cables that are alleged to be "12 Volt cables" cannot handle the load during a hot start issue. The truck has factory manifolds but does have a heat shield on the starter. I did the Ford solenoid conversion before swapping cables but after doing a starter swap at a gas station pump while towing my Bayliner I finally figured out that I needed to go to the heavy cables and that fixed the issue. On that truck less than 20 bucks difference in the price of cables. I learned 62 years ago that you can get away with a few things battery and cable wise on a new car but need to upgrade when you are working on an older car or truck. Older rigs need the best battery that fits in the space and need larger cables for flow than a brand new one can get away with.
I use 1/0 welding cable from the tractor store from the trunk to the inside of the firewall under the dash where I mount the solenoid. Then a regular parts store battery cable that's oil resistant etc through the firewall to the starter. Cranks up small blocks in the dead of winter just fine.
Probably 00 actual Battery cable. I'm not a big fan of trunk/rear mounted batteries but sometimes that is where it has to be. I also like to run a smaller (like 1 or 2 ga) dedicated ground from where it grounds the frame at the rear to the starter. I know that is overkill most likely but I'd rather have more ground capacity than needed than less. A lot of wiring schemes do not think about the grounds. You need just as much grounding capacity as positive capacity.
The answer to the question about why people use oversize wires is really pretty simple from my point of view....... Most of us are not electrical geniuses, and many like myself are what I call "electrically challenged". When we wire something, we don't want to have to redo it later after we spent hours trying to figure out that the wire we selected was too small to do the job.........or worse we immediately found the problem because it melted or caught on fire.........so we use the overkill solution that works for almost everything we build...........use something bigger than what can give you a problem later. When I wired my pole barn, I figured there would be times when several things might be operating on the same circuit and some of those things were machines.......so I wired my pole barn with wire that was larger than the wire for the outlets in my house. Been working just fine for 40+ years that way. So the simple answer is that those of us who are electrically challenged should err on the side of overkill. Those that know far more than we do are welcome to read the directions and proceed according to the experts. I'm good with that because my way works just fine for me.
I agree with what you are saying..........the thing is, if you actually think about what that means........ it would seem to me that all larger gage electrical wire resists abrasion and also has oil resistance. I guess some resist more than others but they all resist............they don't immediately dissolve when in contact with oil or immediately abrade or cut or break when rubbing against something. If someone has enough oil emitting from their vehicle to make an electrical wire have a problem, then it would seem that the oil leak is what needs fixing..........and if a wire is rubbing enough to cut or wear thru...then the mounting of the wire is the problem. I don't mean that as a slight at you, because you were only stating that the wire manufacturer does make wire that is sold as oil and abrasion resistant.............a selling point so to speak. I think most any wire of suitable size, with fine strands for flexibility, and made of copper is going to be covered with pretty good insulation and work just fine for our needs......but then I oversimplify things because I'm electrically challenged.............Someone can probably find an example thats the exception.
I'd rather have a breaker/fuse pop than a wire short and start a fire, wouldn't you? Building cars for customers, you never know what they're going to do. I've seen some pretty dumb shit. That said, you have to assume for the worst and plan accordingly.
Bigger is better, personally I almost always use one size larger wire. Also the longer the run the more voltage drop you get, this is especially true at lower voltages.
A 2/0 cable is going to be an appropriate size for a 12V system from battery to starter. You don't need 4/0. Skin effect only applies to AC circuits. DC circuits will flow current through the entirety of the conductor's cross-section. Current carrying capacity is not related to strand count. An X gauge fine-stranded cable will have the same ampacity as a single-stranded one. Stranding only gets you flexibility in the DC realm.
Those charts are for standard house or commercial wiring, not for fine strand welding cable amperages. Fine strand is more than double what those charts show.
A solid diameter single conductor is the highest amperage rating anyone could find. It's what most high voltage main lines are made of. It's of course too ridged to use for almost any other application. Circular mils will increase the finer the strands are inside one sheath, so fine strand wire does indeed have higher current carrying ampacity because of the lack of gaps between strands. It's about as close as you can get to a solid single wire of equal diameter. But it's not quite the same as a single solid strand.
You do realize that with automotive electrical wire the smaller the number the larger the wire meaning that 2/0 is quite a bit larger than 4/0 Wire?. Just as it is accepted that a 6 volt system needs the larger cables and wires to have less resistance for the 6 volt battery to push th1e amps through a 12 volt battery does better pushing amps though a heavier 2/0 cable rather than a rather skinny 4/0 cable. New cars with every electrical component in the car get away fine with 4/0 cable simply because normally every connection is good and the is a minimum of resistance in the system. Older rigs like my 77 1 ton with a 454 (common hot rod engine) don't always have the best connections, components in the best condition or wiring in the best shape.
That seems to be the way Solar installation folks but I'll damned well guarantee If you load up and go to the parts house right now and look at the 4 gauge battery cable =12 volt and the 2 or 1 gauge cable the 2 or 1 is larger in diameter. I'm tired of fools who frigging go off the wrong information just hauls your ass down to the parts house and look for yourself.
Hold on fellas, were getting crossed up here; Wire numbering has a goofy split at 1 gauge. Starting at 1 gauge and shrinking in size, the bigger the number, the smaller the wire, and going the other way from 1 gauge, that is, 1/ought, 2/ought, etc., it gets fatter.
Oughts are a whole different thing. A 00 is smaller than a 0000. One should not ought to be too testy. I didn’t get testy above when I was schooled about current on the surface of AC vs DC. Hopefully folks who read a thread will read all the words.
Well stated Thank you I learned a few things one of which is welding wire does have a higher amp carrying ability vs standard wire for any given wire ga. due to more wire strands- make sense. Dan
And I’m tired of the fools who fail to admit they may be wrong…yes as the number gets smaller the wire gets bigger until you get to zero then you get into the oughts, which start going up. Obviously you missed that day at the spit and whittle club.
Not sure where you got that info, but it's not correct. 4/0 is much larger than 2/0 and carries far more amperage. What you say it true up to #1 size, but after that the more zeros after the number the larger and higher amperage it is. Check out this chart at Cerowire: https://www.cerrowire.com/wp-content/uploads/2021/04/Cerrowire_Ampacity_Chart_210405.pdf
Did any of you ever wonder how our ancestors came up with some of these downright stupid ways of sizing things ? Think about it for a second. Look at sheet metal........10 gage is thicker than 16 gage Look at Taps and Dies..........fractional sizes till they get down to 1/4" then progressively smaller numbers. Look at drill bits and as they get smaller they quit using fractions and start with numbers......a smaller drill bit has a bigger number. A #80 drill bit is smaller than a #40 and to make matters worse, they used Letters too. Then to top it off they interspersed the letters and numbers between the fractional sizes. It would have all been much simpler it they had just used the decimal system.......everything for drilling and tapping, every sheet metal gage, and even every wire size simply referred to by its physical size. Walk into the store and simply say I want a .312 drill bit and a .375 tap. (yes you still have to look at a chart to see what size drill a .375 tap needs, but you aren't dealing with numbers and letters that have no real relationship to anything). Want some sheet metal. Just walk into the store and tell them what decimal thickness you want.........instead of looking up on a chart to see what .018 thickness is called. Same thing with this wire sizing............would it not have been much less confusing if electrical wire was just referred to by its decimal size and it would automatically get bigger as the decimal got bigger. Yep, I can't imagine how so many of our ancestors all came up with such stupid identification systems. Now, real quickly, a couple test questions.................. Whats the diameter of a # 1 drill bit ? Whats the diameter of a .228 drill bit? Whats the thickness of 18 gage steel ? Whats the thickness of .047 steel ?
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