Does Gauge of Ground Wire Matter

[Mikeinnj]

This is a solid copper ground strap originally used on Model A Fords.
The originals were covered with solder to prevent corrosion.
This strap is available at Brattons Model A Supply as well as the negative cloth covered cable that runs from the battery to the starter motor switch and is of the original gauge.

[Big hammer]

Originally Posted by Mikeinnj

This is a solid copper ground strap originally used on Model A Fords.
The originals were covered with solder to prevent corrosion.
This strap is available at Brattons Model A Supply as well as the negative cloth covered cable that runs from the battery to the starter motor switch and is of the original gauge.

Later model A's used a braided ground cable, the solid ground strap was for earlier A's.

[katy]

Originally Posted by Aarongriffey

Welding cable is larger than battery cable.

Like my underwear, it depends, welding cable is available in sizes #6 AWG to 4/0

[rotorwrench]

Voltage is a carrier so the amount of voltage in a line is what makes the difference. Low voltages like 6-volt have to have less resistance in the line so that there will be very little line loss plus the voltage affects the amperage draw of a given load according to Ohms Law. This is why 6-volt requires at least one normal size of larger wire gauge with larger size fuses to protect that wire size if fuses are used. Many manufacturers used no wire protection back in the day but there used to be a lot of car fires due to that too.

If you have a spark when connecting a ground cable, it means there is already a load in the circuit. If all electrical loads are turned off, there should be no spark at all when connecting or disconnecting the ground. On the power side (negative side on the old Fords), there is an inrush when connecting it if the ground side is connected so it's not uncommon to get a spark on a power cable. This is why most folks disconnect the ground side first. Polarity really plays no part in this. Manufacturers designed most switch circuits to switch the ground side of a load to protect the switches from arcing.

[bob from red oak]

this post is a bit late but when I put the disconnect on my A I bought the heavy wire at Tractor Supply. The had several different lengths,

[jg61hawk]

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[Ranchero50]

Voltage most certainly matters.

E=I/R is the equation.

Halve the voltage (E) and you need double the amps (I=current) to run the same starter resistance load (R). Increase the load with smaller cable and it takes more amps to do the same work.

Think of voltage pushing amps through resistance.

[DHZIEMAN]

Originally Posted by jg61hawk

I bought a disconnect switch locally, the type with a big turn dial OFF/ON. They only had normal 12volt wire in the store. I am breaking the POSITIVE ground. Will it matter if I run the 12volt wire from the frame to the disconnect and then the good 6 volt wire from the disconnect to the battery?

Do ground wires carry current or is just the Negative wire from the battery to the starter the important one?

If the answer is the ground wires need to be 6 volt, do they make a 6 volt disconnect versus a 12 volt disconnect?

Basically, the ground wire needs to be the same gauge (current carrying capacity) as is the other cable on the battery! Some of the old vintage battery cable is almost as stiff as rebar, but it is sized that way for current capability, and the ground wire carries the same current.

[katy]

Whatever goes out of the battery on one side, + or-, has to come back in on the other side. So all the battery cables should be the same size. Simples.