Battery Cable/Ground Strap Gauge Questions

[leo]

In layman's terms for the electrically challenged what cable gauge is required for good Model A service? I never see any of the replacement ground straps rated by gauge and I would think the size being used for the negative cable should be the same as the positive. Then there is the length issue. I'm including a master cutoff switch in my battery configuration so the connection one side of the switch to the frame is short while the connection from the other side of the switch to the positive terminal is much longer, maybe 20 inches.

[MikeK]

You need #2 AWG. That is what Ford used originally. NOT the much heavier 2-0, 00, or "two-aught" that many confuse with #2. If you are running 12V then #4 AWG is good.

In any case, as long as you are re-working the ground wiring, an added lead from the same center crossmember bolt one side of your switch is attached to, going to a tranny bolt is a good idea unless the car is a fine-point resto.

[leo]

Hey MikeK, thank you, so #2 is good. I was working with #1 and it was difficult. Reading previous posts it appears there is much disagreement about battery cable gauge, sounds like bigger is always better.....

[Tom Wesenberg]

Bigger is able to carry more amps, but as Mike said #2 if a better choice because it's plenty large and can be worked with much easier, as you found out. The weak link will be a poor quality master cutoff switch.

[Aok]

I have a additional ground wire (forget what gauge maybe 1) from the battery connection on the frame to where the starter bolts to the frame.

[CarlG]

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Originally Posted by Aok

I have a additional ground wire (forget what gauge maybe 1) from the battery connection on the frame to where the starter bolts to the frame.

...

[Aok]

Originally Posted by CarlG

...

Ok to the clutch cover/bell housing.

[Mike V. Florida]

#2 AWG will handle 181 amps in chassis wiring according to the Handbook of Electronic Tables and Formulas for American Wire Gauge.

A 2 foot length of #2 wire drawing 100 amps will lose .064 volts

[leo]

Which in laymans terms means?

[Kurt in NJ]

You want less than 0.5 volt drop between the battery and starter
the starter locked about 500 amps, cranking about 225 amps---
according to the posted ratings for #2 wire if the total length of wires from the the battery to starter is under 2 feet it will probably be ok ----and the switch should be rated for over 200 amps

[700rpm]

Can someone please post a photo of their auxiliary ground strap, from battery to trans, for 6v?

[leo]

Kurt in NJ, the Cole Hersee switch appears to fall within your limits for 6 volt applications.

[Marshall57]

Originally Posted by 700rpm

Can someone please post a photo of their auxiliary ground strap, from battery to trans, for 6v?

I'm looking to glean some ground strap info also. I like the idea of going from the started bolts to the ground bolt on the frame. The length might be a little longer than I was thinking of using. Anyone else solved this problem and has a photo or a really good description?

[Terry, NJ]

Recently, I had an occasion to put an auxiliary ground between the frame and the bell housing and the starter. The starter now spins better. I put it on the opposite side of the frame flange, using the same bolt. The other end, I put on the the bell housing. And as I said, The starter spins faster now. It worked so good, I put one one the other two cars I own.
Terry

[Terry, NJ]

This is a very simple addition. I even used a 12v cable in one car, since it is an auxiliary cable and not a main pathway, it works but I'm not recommending it. One I even used an old , but very heavy aluminum cable from an old Piper Tri pacer. All worked well! I used the same bolt through the frame to secure the cables, one cable on top of the flange and one on the bottom. The other end went to the nearest bolt on the bell housing, to keep the cable as short as possible. There is definite improvement.
Terry

Originally Posted by 700rpm

Can someone please post a photo of their auxiliary ground strap, from battery to trans, for 6v?

[Terry, NJ]

I suppose the longest cable ever used in a car (at least of any that I saw) was the neg. cable (6V pos. Grnd) used on the 49-51 Fords. This cable was the starter cable from the left side, down the frame, under the engine and then to the starter. Roughly 5 ft in length. This did not appreciably harm the flow of electrons so maybe we're dwelling on length too much.
Terry

[ian Simpson]

Originally Posted by Terry, NJ

I suppose the longest cable ever used in a car (at least of any that I saw) was the neg. cable (6V pos. Grnd) used on the 49-51 Fords. This cable was the starter cable from the left side, down the frame, under the engine and then to the starter. Roughly 5 ft in length. This did not appreciably harm the flow of electrons so maybe we're dwelling on length too much.
Terry

I do not think that was the longest - The positive cable on our negative ground MGB is longer as was the one in my 1968 Austin Mini. The battery in an MGB is under the floor behind the passenger seat and the one in a 68 Mini is in the trunk.