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Alrighty. My '37 120 (still 6V) starts great. It currently has 2/0 cable running from the positive terminal to the starter, and a braided ground. I have a Cole-Hersee shutoff switch to install (the BIG one), and want to switch my positive battery cable to the correct appearance braided one.

I ordered the wrong parts for this job a while back, but never did it. I ordered 1/0 cable.

Do I order 2/0 braided cable, or do I run the 1/0? Thanks in advance!

Edit - I understand 2/0 is bigger. Looking for any practical experience with 1/0 before I waste a bunch of money buying new parts if what I have will work.

E = IR


Mr. Ohm is your friend. As is Google.

Good Evening...Double 0 (00) is what you really should have for a six volt system. Ernie in Arizona

2/0 is a larger cable size than 1/0 and will handle higher current. At 75 degrees C, 1/0 is rated for 150 amps continuous and 2/0 is rated for 175 amps continuous. I’m not sure what the short duration ratings are.

I’m not sure what the current draw is. Obviously, when starting it’s much higher than the continuous ratings.

Without knowing the current draw, the safe thing to do would be go to with 2/0. That said, if you can find the current draw and the short duration rating of 1/0, you may find that the 1/0 is sufficient.

The other thing to consider is length. As you know, longer the run, thicker the cable should be.

The original cables were 1/0. Been OK by me for the last 50 years.

Quote:

Awesome! Thanks Ross.

Ken_P

I personally use 2 aught welding cables with soldered ends. I’ve yet found a source for a braded ground strap in the same size, so I’ve done the unspeakable and used the ‘round stuff’ for the positive side. I just bought an aught ground strap that may become a second ground path for the chassis, or perhaps I can make the braded cable obvious, and the round one well hidden.

As for a disconnect switch, I bought, fortunately long before the price went to the moon, an Eaton/Bussmann unit rated at 400/2000 A. I happen to disconnect the positive side, but that was driven by the available ‘under hood’ space and the proximity to the positive terminal. I suspect each of us will have several opinions on which pole to disconnect when the car is in storage. The battery terminals that attach to the battery itself were bought from DelCity, and are made from a brass alloy. The bottom line is the terminal remains in the elastic range when clamping onto the SAE terminal, that is, as soon as the pinch bolt torque is released the terminal is free of the post. Because of this the extra cost of a disconnect switch may not be needed if you are willing to ‘pop’ the cable free of the battery.

I’ve also found that a battery rated between 800 - 900 CCA will provide adequate starting voltage/current if used in conjunction with the above cables. Let’s not forget the other opportunity to undo all of our good intensions, namely the solenoid contacts. I swear I ‘fixed’ a ’54 327 by installing a rebuilt solenoid . . . even though the removed unit did not look all that bad with respect to oxidation/corrosion/pitting. Perhaps I should have soaked the copper washer in solvent for a few days, or used the ultrasonic cleaner.

I agree with Ross, in that when these cars were new and driven regularly 1/0 cables were adequate, but it is an industry that notoriously saved pennies on every part. Ross’s experience aside, I don’t used my hobby cars anywhere nearly as frequent as I would prefer and seem to be presented with a car that hasn’t been used for 3-4 weeks. The self-discharge rate of a battery is temperature dependent, and hot storage will maximize the self-discharge rate (I got that factoid from Harley Davidson). I live in Arizona so it’s an up-hill battle of battery voltage that is less than I would prefer, and an empty float bowl . . . which I refill with the auxiliary fuel pump prior to attempting a start. The garages where the cars are stored does not have electrical service, so for me every little bit of voltage drop is important. Knock on wood, I’ve owned these cars for over 10 years (zero experience below 40F), and have never had a case where the engine didn’t start.

I believe when Georg Ohm published his work he advanced a slightly more complex relationship than we use today, and his contemporaries didn’t completely believe him.

dp

Packard in the service manuals specified a size no smaller (= larger number) than #1 for the 6 volt cars.

Making sure that, for example, you are not clamping the ground cable to a rusty engine block with a rusty screw, will often be more important than say, switching to a 00 cable from 0.

There will be two braided ground straps on a '37. One between the battery and the frame and another between the transmission case and the frame. Both of these are relatively short.