In case anyone is interested, here is an image of the positive battery cable harness that runs from the engine bay to the trunk.
I know it would add weight, but I'd be tempted to make it far bigger and thicker, like locomotive power cable, which is also pretty limp and has some tough insulation on it.
In November 2009, there was Customer Satisfaction Notice J21, Hot Start Engine Cranking that affected 15,500 cars. The notice required the replacement of the battery ground cable and an upgraded 730 CCA battery (to replace the 625 CCA battery). The parts were as follows: Ground Cable Package- CECOJ210AA Upgraded Battery- BB4R750AA I had this work done on my 2009 SRT.
Ah, so. Here begins some electrical theory few realize. A ground lug is attached to the car body. The ultimate lower limit of its resistance to current flow is defined by two things: A) the outer circumference or boundary of the lug where it contacts the car's body B) the thickness of the car's body at that point. As an example, you have a lug which, conveniently, is 1cmX2cm where it contacts the car's body. The car's body is 1mm thick steel. This means that ALL current going through that wire HAS to travel through a 1mmX1cmX2cmX1cmX2cm boundary of steel before it can access the ground lug itself. That is 1mmX(1+2+1+2)cm, or 1mmX6cm, aka 1mmX60mm, or 60 square millimeters. It doesn't matter if your ground cable itself is a thick, one-inch industrial cable. It doesn't matter if it is infinitely thick. All current going through that wire has to go through 60 square millimeters of car body steel to "break" the perimeter to enter the zone where the lug is in contact with the car body. The car body has a higher resistance than copper. A material's resistance to electrical current flow is measured as follows: https://www.electronics-notes.com/a...ce/electrical-resistivity-table-materials.php Copper is 1.7X10^-8 ohms for a cubic meter. Iron is 1.0X10^-7 ohms for a cubic meter, or SEVENTEEN TIMES greater than copper. But, the flow is going through 60/1 million square millimeters, to find the proportion to a square meter. I am merely speaking of the boundary between the car body and the lug, here, not the volume inside said boundary. Thus the resistance of said boundary is (60/1,000,000)/(1.0X10^7) ohms, or 600 ohms, IF the boundary were a meter long, but, that boundary is not 1m long, or resistance would be truly atrocious. Let's average out the travel of an electron from the steel to the lug: Since the lug is 10mm wide and 2mm long, the electrons at the tip have to travel 2cm to get to the copper ground wire, and the electrons at the part closest to the copper have to only travel half a centimeter to go from edge to center. Average travel, very roughly, is 1.25cm. So 600 ohms/ meter for a that boundary for 1.25 versus 100cm give us 600/(1.25X100)=3.84 ohms. This may not seem to significant, and for most purposes it is not. However, if one is using 200 amps of power (aka about 2400W) to run one's starter or stereo, whichever is using the lug, then you encounter a juncture-warming 768W of electrical heating. Most systems don't crank the engine very long or play a long, continuous bass note at 2400W, so there is little risk of making a very hot spot on one's sheet metal, but that one spot is the highest resistance point on the entire grounding setup of the car. Then, why not just ground the same cable at multiple points all over the car? Because then you risk getting what is called a "ground loop" where the current flow fluctuates between the various grounding points, which can, in theory, create radio noise. The car body itself carries current around itself very well for it intended use, so a ground wire is not run from the rear of the car up to the front, to avoid ground loops. Also, the cable for the positive part of the battery terminal connection is longer than 1.5cm, so it is profitable to make it larger, as larger conductors reduce radio noise and electromagnetic interference, as well as resistance to current flow between battery and accessories, and between generator and battery. If, for example, the positive wire is 1 gauge, not to be confused with one-ought(1/0) then it has a resistance as shown on this page of https://www.rapidtables.com/calc/wire/wire-gauge-chart.html of 0.1236ohms/1000 feet, or 0.0017304 ohms, a negligible amount. Even at 200 amps, this is only 0.34 watts of power loss or so. So, the highest-per-mm resistance in the system is through the steel car body just prior to the ground lug, and the copper wires are absolutely minimal. If you want lower system resistance, bare an area of steel on the car body equivalent to your (preferably long and wide) ground lug, and through-bolt it solidly in a few locations just to ensure proper contact. You can use multiple ground lugs, also, as long as they are the same distance electrically from the battery ground terminal, as twice the ground lugs equals half the resistance.
