Obviously a 6" piece of 10 will carry more than a mile of #1.
Had a guy in here about a week ago (more or less) that was having starting problems...
Load tested the starter solenoid and starter cable, but it was pretty obvious before that it was a battery terminal/battery cable problem...
So, instead of doing what I recommended, he purchased a discount store battery cable...
Still had the same problem, more or less.
Finally he gave up and brought it here again.
Took off the discount cable, tested it for connections, no resistance to speak of...
Load tested it, and it failed miserably.
Started stripping insulation, First off, it was supposed to be a 6 gauge wire, turned out to be about 9 gauge actual...
And at one point about three inches from the battery terminal, the wire was frayed down to two strands...
The guy kept saying that he 'Saved' $11 dollars over the cable we wanted to build for him...
Here is the kicker, the local 'Auto-Jerks' wouldn't take the cable back because we had removed parts of the insulation!
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Obviously a 6" piece of 10 will carry more than a mile of #1.
True!
Resistance builds over distance with DC current.
Doesn't matter how much voltage you put in, at distance you can't get any amperage out because internal resistance will have consumed it and expelled it as heat.
The reason Edison's power plants never took off is because you can't push DC current long distances.
Just over a mile from the generating station you will get nothing usable, and low voltage DC generators were EXPENSIVE to build and a nightmare to maintain!
AC current will transmit over hundreds of miles and the generators are much easier to build and much stronger designs...
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As to the original question, before the thread got 'taz-e-fied'...
The reason for an alternator not getting a good ground, or anything else for that matter...
Is easy!
You are tring to drive electrons through things that don't conduct electricity very well, or in some cases at all.
Paint, rust, mud, loose fasteners, steel, cast iron or aluminum are all horrible conductors of electricity.
Most jeeps have a 'Ground' wire that connects to the engine block or the alternator bracket.
This is a 'Median' location to save the cost of a proper ground wire to all systems.
Now, you have a copper wire...
(I hope! Some of you have steel woven straps!)
Connecting to a steel bracket or iron block or head via a rusty bolt...
This single undersize connection is supposed to supply 'Ground' to the largest consumer in the system, the starter.
How may steel to iron to aluminum connections via rusty bolts, through poorly fitting spacers and engine gaskets is there in that 'Circuit'?
Lets see, The rusty bolt that connects the wire to the head or bracket, in the case of the bracket, the painted steel bracket it's self, then through the paint again to a bolt to the cast iron head or rusty bolt to the oxide coated aluminum alternator housing, then to another rusty bolt to the voltage regulator & rectifier,
OR,
In the case of the starter, through that second coat of paint to the rusty bracket to head bolt, then through a cast iron head to the rusty and sealer coated head bolts,
Then to the cast iron engine block...
The head gasket will keep a direct head to block connection from happening...
Then through a rusty bolt to an oxydation coated aluminum bell housing, then through another rusty bolt to the aluminum starter frame, then through another bolt to the steel starter housing, then through another rusty starter bolt to the starter windings...
Anyway, you get the idea...
Run a dedicated, large gauge ground to the starter housing directly, since this is where the largest draw is going to happen...
Run a heavy wire (8 or 10 Ga.) to the alternator housing so the device that creates every electron your vehicle uses can function properly.
It's also a good idea to ground the engine it's self...
You have gauges that require an adequate ground to function properly.
Since the engine ground usually supplies the ground to both the primary and secondary sides of the ignition, it's a good thing for them also.
In addition, the front grill needs a dedicated ground for the front lights, electric fans, ect.
The rear needs a dedicated ground for the rear lights, trailer hookup, fuel tank sender, ect.
The dash needs a dedicated ground so your wipers, dash lights, radio & other accessories work correctly and to the best of their abilities.
Grounding the frame and drive line is a wonderful idea...
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Guys argue this all the time, but the facts are NOT in dispute...
FACT.
The factory employs people to figure out how to use the least amount of materials and make the least amount of connections in order to 'save' money.
FACT.
What passes for 'Ground' in most vehicles means the engineers have decided what the absloute LEAST they can get by with and still have the vehicle live through the warranty period.
FACT.
The factory didn't use the best of anything.
And now those 'Good Enough' parts are 25 to 40 years out of warranty...
FACT.
If you have the knowledge, and you look around a little, you can do so much better with the replacement parts you use...
FACT.
If you were only interested in using the factory components, you wouldn't be looking for a better way to do things and wouldn't be here asking questions and (hopefully) learning something.