Where to buy 4 ga. Alternator wire....20 ft?

[Baron Von Crowder]

sounds crazy to me

substantially less likely to short a wire and catch on fire.

[Mach1]

substantially less likely to short a wire and catch on fire.

true that

[BERNIE MOSFET]

substantially less likely to short a wire and catch on fire.

Don't run your wires through the oil pan and fuel tank and it won't be a problem!



I say it is good practice, but with caveats.

[BERNIE MOSFET]

I am pretty sure that it is referred to as a "Floating Ground SYstem"

Ground is a relative term.

In an abstract sense, it is a zero reference for quantifying the strength of an electric field. It's a similar concept to taring a scale in that you are establishing a zero point from which to measure. Electric Potential is a way to describe the strength of an electric field and potential difference is the difference between two points relative to each other in an electric field. Volts is the unit we use to quantify the difference. That's why you can measure the voltage from "source" to ground or the voltage across a physical device in a circuit. These are points in an electric field that you can measure.

In a physical sense, ground is the source of electrons, not a destination. This is distinct from an electric field source, as above. In this way, a single point ground is a single source of electrons. Automobile grounds are floating in the sense that they are not an earth ground, meaning that they may have a different potential than earth ground - the two are electrically isolated by the tires. The electrons come from the battery or the chassis, itself.

By pulling from multiple sources of electrons within a single circuit, a second potential difference can be introduced - resulting in a voltage between the sources. This can happen for a number of reasons that I won't go into here. If the two sources are not isolated, the voltage results in current flow because the two sources are actually a source and a destination relative to each other. This is what ground loops are.

In systems where RF concerns outweigh the possibility of DC ground loops, multiple ground locations are ideal although the physical designs have to take into account current return pathways so as to minimize the ground loop effects.

Since automotive systems are DC, and RF interference between systems is not a primary concern, a single point ground established at the negative terminal or a bus bar connected to the terminal establishes a single ground plane is not a bad idea. As I said, multiple chassis connections can introduce potentials at different ground locations if they are not electrically isolated. The thing you don't want to do with more modern automotives is connect signal and power grounds together at a common point because you will introduce noise to the signals that way.

This is why it is good practice but not always best practice. However, as DJ notes, good practice also dictates that wire routing take environmental considerations into account - you don't want to introduce greater likelihood of failures because electrical engineers like to do things that look good on paper. Mitigating factors for single point are routing so as to prevent chafing and using wiring with insulation that withstands greater temperatures and exposure to petroleum products. Mitigating factors for multi point is good electrical bonding at common points and electrical isolation between ground points.