Battery Cable Size

Wed Jan 18, 2012 6:49 pm

It's too cold to go fishin' around here right now but I am going to open a can of worms anyway.

I have been watching the latest threads about batteries and cable sizes. As is typical, there are always opinions on cable sizes so I am curious. Some guys say 1 or 2 awg is fine for six volt cables while others say it should be 1/0 or 2/0 awg. 2/0 is pretty hefty wire so I am wondering if that is right. TM Tractor Parts sells 6v cables that are 1 awg, is that big enough? I have about 50' of new 1 awg welding lead that I was told would make excellent battery cables because of its pliability (I know, the insulation breaks down easier).

Would any of these four sizes be suitable for 6v? I know bigger is better, but would a guy who is using 1 or 2 awg have problems and should he remove it and replace with 1/0 or 2/0 wire? If TM sells 1awg it I would think it is sufficient.

I don't want this to be a debate on where to buy the best wire or why converting to 12v is better or what the weather will do to any particular wire. That's not what I'm after, I'm just curious as to what wire would be okay if an owner already had it on their tractor.

Re: Battery Cable Size

Wed Jan 18, 2012 6:52 pm

My preference overall I guess would be for 1/0 but I have no problem using 1 gauge on a cub.

Re: Battery Cable Size

Wed Jan 18, 2012 7:08 pm

I use 1/0 but i would suspect the small wire would be ok unless u have a hard starting situation where there is prolonged cranking .Just my opinion.

Re: Battery Cable Size

Wed Jan 18, 2012 7:23 pm

I use #1 welding lead. Rated for about 300 amps and the best part, very flexible as you mentioned. About $2.00/ft. in these parts. And I should add that I have used this on a 6v tractor for over 5 years with no issues.

Re: Battery Cable Size

Wed Jan 18, 2012 8:03 pm

When dealing with a 6 volt system the problems/downsides to using smaller sized cables is the increased resistance which means a drop in the actual current/voltage that would be going to your starter. Less current means a slower cranking speed at the starter motor and increased resistance means heat (worst case scenario=fire). Most (but not all) problems with a slow cranking speed in a 6 volt system can be traced back to one of a few things; Losse or dirty connections (including brushes in the starter motor), wrong sized battery cables (power and ground) or a weak or undersized battery.

It is usually this slow cranking speeds that make most people want to switch from a 6 volt system to a 12 volt system, at least this is the case when dealing with antique cars, I am still relativly new to tractors however so I can not comment. When a 6 volt system is in good operating condition there is no need to make a change over to a 12 volt system. A 12 volt system is no more reliable than a 6 volt system or vice-versa, they are just different voltages. One problem that new owners of antique equipment have with a 6 volt system is the fact that it is usually their first experience with a 6 volt system and it cranks slower than their modern car. This is very true, it does crank over slower, it is a different system and it is working how it was designed to work, but not like the modern equipment that they are used to.

Smaller cables will work but larger cables will work better. I must admit that when I replaced the original wiring harness on my 1952 cub, I did not pay attention to the gauge of the battery cable, the insulation was worn and frayed so it got replaced, it hangs on a hook in the garage so I will haveto check the gauge of the original cable. The new cables that were made (both ground and power) were out of 2/0 cable. That is one point that is often overlooked, the power cable to the starter and the ground cable need to be made out of the same gauge of cable, you must have the same amount of power coming and going.

One thing is certain, the cables that you get at most auto parts stores for a 6 volt system are 2 awg, not 2/0 awg (double 0 or 00), and are too small for a 6 volt system and in my opinion should not be used on a 6 volt system (but that is just my opinion). Like I had said at the start of this paragraph, smaller cables will work, so your 1 awg cables will work and definitly be better than the 2 awg, but the 1/0 awg would be even better. Some of the big Packard, Cadillac and Lincoln motors (V-12's & V-16's) came from the factory with 4/0 awg cables and were 6 volt systems. You can hold onto a 2 awg cable while cranking an engine and feel the temperature increase, quickly. Using larger cables reduces the resistance and the rise in temperature. In a nutshell;

Smaller cables= higher resistance and lower cranking speeds
Larger cables= lower resistance and higher cranking speeds (system functiong as designed)
2 awg- don't use, and if it's on there I would replace it
1 awg- works
1/0 awg- works very well
2/0 awg- works even better
It's your vehicle/tractor, do with it as you please just please do it safely.

Re: Battery Cable Size

Wed Jan 18, 2012 10:12 pm

Iam going to try a #2 cable Rated 600 VOLTS I just solidered new ends on it today.

Re: Battery Cable Size

Wed Jan 18, 2012 10:32 pm

Voltage rating is pretty meaningless when dealing with old vehicles. Voltage ratings apply to the insulation. A #2 wire with a 600V rating will conduct no more current than one with a 20V rating. Wire gauge (size or diameter) and current ratings are what matters.

Re: Battery Cable Size

Thu Jan 19, 2012 4:58 pm

The advice to use 1/0 or 2/0 cable comes from the larger tractors like the H and M.

A Cub doesn't start that hard, and cables that heavy are really a waste of money. #2 is more than adequate on 6V.

Re: Battery Cable Size

Thu Jan 19, 2012 5:14 pm

The difference between a #2 ga. cable and a 1/0 ga. cable will make a world of difference in below freezing temperatures. Even with a cub. The colder it gets, the more difference.

Re: Battery Cable Size

Thu Jan 19, 2012 5:21 pm

Well, the can has been opened, I might as well go fishing. I think I have enough info to know that I can use the rest of my 1 awg wire and on my next trip to the cable store I will pick up some 1/0.

Thanks for the answers.

Re: Battery Cable Size

Thu Jan 19, 2012 6:22 pm

I don't know a lot about cable sizes and current flow, but I was told once that the current flows over the wire not threw it. If this being so I would think that a 1 AWG welding cable that has a lot more strands in it may be as efficient as the 1/0 battery cable.

Re: Battery Cable Size

Thu Jan 19, 2012 7:22 pm

Radio Frequency current moves over the wire. low frequency AC and Direct Current move through the wire.

Re: Battery Cable Size

Fri Jan 20, 2012 3:10 am

Criswell wrote:When dealing with a 6 volt system the problems/downsides to using smaller sized cables is the increased resistance which means a drop in the actual current/voltage that would be going to your starter. Less current means a slower cranking speed at the starter motor and increased resistance means heat (worst case scenario=fire). Most (but not all) problems with a slow cranking speed in a 6 volt system can be traced back to one of a few things; Losse or dirty connections (including brushes in the starter motor), wrong sized battery cables (power and ground) or a weak or undersized battery.

Smaller cables will work but larger cables will work better. I must admit that when I replaced the original wiring harness on my 1952 cub. The new cables that were made (both ground and power) were out of 2/0 cable. That is one point that is often overlooked, the power cable to the starter and the ground cable need to be made out of the same gauge of cable, you must have the same amount of power coming and going.

One thing is certain, the cables that you get at most auto parts stores for a 6 volt system are 2 awg, not 2/0 awg (double 0 or 00), and are too small for a 6 volt system and in my opinion should not be used on a 6 volt system (but that is just my opinion). Like I had said at the start of this paragraph, smaller cables will work, so your 1 awg cables will work and definitly be better than the 2 awg, but the 1/0 awg would be even better. Some of the big Packard, Cadillac and Lincoln motors (V-12's & V-16's) came from the factory with 4/0 awg cables and were 6 volt systems. You can hold onto a 2 awg cable while cranking an engine and feel the temperature increase, quickly. Using larger cables reduces the resistance and the rise in temperature. In a nutshell;

Smaller cables= higher resistance and lower cranking speeds
Larger cables= lower resistance and higher cranking speeds (system functiong as designed)
2 awg- don't use, and if it's on there I would replace it
1 awg- works
1/0 awg- works very well
2/0 awg- works even better
It's your vehicle/tractor, do with it as you please just please do it safely.


I also have seen that using 2/0 welding leads and adding extra ground straps on computerized, high compression cars actually increased HP and coil voltage. Now it was only a few extra horses BUT when you spent $10,000 on just the engine, I think $1-200 more to help starting, stereo AND ENGINE PERFORMANCE is worth it... now that said is it worth an extra $20 to you to make sure your cub starts ??? Well if your in the South you might not need it but if your trapped in a snowstorm in Minnesota its worth $100's

Re: Battery Cable Size

Fri Jan 20, 2012 3:30 pm

I live in western New York where it's often very cold at snowplowing time. Using 2/0 cable sounds good to me. It was stated that most auto parts places don't have that size. Is welding cable the only alternative, and if so, is there any problem with using it? Will welding supply places sell relatively short pieces like I would need?

Many thanks for all answers.

Re: Battery Cable Size

Fri Jan 20, 2012 4:33 pm

I just replaced the cables on my '58 lo-boy. The positive cable was about 5 1/2' long. I thought it'd be tough finding the long cable but Auto Zone had it and the 12" neg side cable in stock and for under $20. They are both the smaller 1/0 which I wondered about too but they are used for car engines so I gave them a try.
incidentally they are both black which I believe is correct. My Lo-Boy has a 12 volt conversion which I rewired last winter with new alternator coil etc...
The exception to being 12 volt is a 6 volt starter that I just redid with a kit off ebay.
I did the work on the starter the same time I replaced the cables.
Got to say I held my breath when I first pulled the rod but it works great. The smaller 1/0 cables are fine the engine cranks fast and fires great and has done this when the temps have dipped to the high 20s. I have zero starting problems now.
Mike.