Battery Cables: Proper size and Proper Terminal ends

[desoto1939]

I recently dug out an older catalog that i had from The Autolite Battery corporation and in one of the sections it talks about the Effect of Cable Size on Cranking.  It shows the various sizes of cable and then lists the amount of current each size cable will carry and how that gets diminished as you go to undersized cable.

 

It also talks about the proper terminal ends and the application of grease and not using grease on the terminal ends.  Basically they do not recommend brass or bronse terminal ends because they will corrode faster then the lead type and if using the bronze or copper coated with grease if they have lost their lead coating.

 

For you new antique car and truck owners the information is a must read to understand the difference between 6v and 12 v battery cable and why you need the larger cable.

 

The entire catalog is very interesting to read  Here are the two pages on battery cable.

 

Rich Hartung

Desoto1939@aol.com

Battery Cable Size.pdf

[JBNeal]

For zero problems cranking, go with 0 gauge

[maok]

Cable size is not dependent on the  battery voltage, it's dependent on the engine size.

[Sniper]

24 minutes ago, maok said:

Cable size is not dependent on the  battery voltage, it's dependent on the engine size.

 

 

It is dependent on current draw, period.  For a given amount of work a higher voltage will require less current, which is why 12v systems have smaller battery cables and 6v systems have larger ones.  It has absolutely nothing to do with engine size except in the most tangential manner, in so much that a larger engine may require more power to start than a smaller one, all else being the same. 

[maok]

Yes, definitely current draw, but current draw is dependent to the resistance to the starter motor pinion gear, ie. engine size, compression, etc.

What happens when the starter motor gets stuck? Current draw increases dramatically, nothing to do with battery voltage.

 

Actually, a 12 volt battery on a 6v starter will draw slightly MORE current than with a 6 volt battery in the same engine because the starter spins faster with 12 volts (than 6 v) and hence slightly more friction is created in the engine. Do the experiment, use a clamp meter over the battery cable and see the results yourself.

 

Current = torque 

Voltage = spin speed.

 

Modern engines with 12 volt starter motors have hi torque gearing, less friction,  are better balanced and designed to start within the first stroke hence do not need the cable size of yester-years.

[Sam Buchanan]

I'll get the popcorn popper going.... 

[maok]

To add to my example of the starter getting stuck, imagine the opposite, ie less load on the engine - remove the spark plugs, remove the fan and the accessories that attached to it, remove the flywheel (actually this not possible because starter turns the flywheel), the current draw will be dramatically reduced because there is less resistance to the pinion gear turning of the starter motor.

 

People often complain about the 'starter is now turning slow' and the automatic response from most is 'you need larger battery cables', even though it was turning fine before. The article above talks about battery terminals and corrosions, which is the most likely cause of these issues and the status of the battery. Battery cables don't reduce over time but  corrosion, terminal and battery quality do.

[Sniper]

Tell you what my 12v converted 51 runs normal 12v style 4 ga automotive battery cables but according to you that's wrong  because a 12v system will draw more current, lol.

 

Watts are watts and regular old electrical theory quite regularly and repeatedly shows that when voltage goes up current goes down for the same power requirement and nothing has changed in regards to the load on the starter when you go from 6v to 12v. 

 

 

 

 

 

[Slickster]

Compression ratio really affects cranking requirements....

[Sniper]

8 minutes ago, Slickster said:

Compression ratio really affects cranking requirements....

 

Changing from 12v to 6v doesn't affect that, the mechanical load on the starter remains the same regardless.

[Sam Buchanan]

I have suggested battery and starter cables that are sized for our 6v systems in several threads. I think it would be helpful to avoid comparing apples to oranges.

 

For sake of discussion, let's limit this 'debate' to the flathead engines with stock specs found in most of our old Mopars. Veering off into compression ratios, large displacements, etc is just a smoke screen when discussing large-gauge cables for our six volt, flattie systems.

 

As Sniper mentioned, the need for larger gauge cables to accommodate the large current loads of our 6v starters is simply a matter of established physics. The only time I've suggested upgrading cables is when I've seen photos of 6v engine bays with wimpy little cables that are customarily used on 12v systems. If the starter, ignition components and battery are suspect those items must be brought back up to spec before larger cables will work to their full potential (pun intended...).

[maok]

21 minutes ago, Sniper said:

Tell you what my 12v converted 51 runs normal 12v style 4 ga automotive battery cables but according to you that's wrong  because a 12v system will draw more current, lol.

 

Watts are watts and regular old electrical theory quite regularly and repeatedly shows that when voltage goes up current goes down for the same power requirement and nothing has changed in regards to the load on the starter when you go from 6v to 12v. 

 

 

 

 

 

 

Mate, do the experiment, you seem like a person who needs to know, with a scientific curiosity. Measure the current (with a clamp meter) with your 12 volt battery/4ga, do 2ga, and do 0ga. Now swap to a 6 volt battery do the same and compare. Apples for apples.

[Sniper]

I don't need to do any of that.  I have been in the electronics business for decades and both my experience and my training already inform me of the answer.  So you can say I already know.

 

 

[maok]

The thing is, your use of the power equation (P=VA) is misused.

 

The power (watts) is higher with a 12v battery than a 6 volt battery because the 12v battery causes the engine to spin faster.

[maok]

I had a similar discussion a few years ago on the aaca forum with a member there (IIRC Bloo), a very knowledgeable poster. He did the swap in his '36 Buick(IIRC) and was surprised that the results weren't what he believed to be. He noticed the slight increase in amp draw with the 12 volt battery.

[desoto1939]

Basically what I was trying to originally when I posted the information was trying to provide some education to any new owner that has a 6 volt car or truck and to provide them with information as two why to use the larger cables instead of the standard 12 volt cable that everyone goes and purchases at their local NAPA or AutoZone store.

 

By showing the information they might understand the reason for the larger cable.  I have another Auto-Lite Wire and able catalog and Autolite recommended  Size 1 for all of the  Pre-war and Post war cars upto 1948 this catalog only goes to 1948 and stops but we all know that the same cable would be used until they switched to 12v electrical systems.

 

I also just scanned two pages from my MoPar factory parts catalogs two pages for Starter and Ground Battery Cable also note that Mother MoPar used number 1 cables.  But also note that on the starter cable they had a section of the cable that was covered with an external spring wrapping just like on the original brake lines where they were exposed to potential damage.  The ground cable did not have the extra coil of outside spring protection.

 

So the next time you go to an AACA car show that is judging cars look real close at the battery cable to see if they have the correct cable with the spring covering probably 99 percent will not have the correct cables.  So education is important to know how out older cars were delivered from the factory. So when Hershey states that they are looking for cars like they came from the factory I really doubt that there ever is a 100 point car because of the small little items that have gotten overlooked or know one educated the judges on this area.

 

The file was too big to  load but if you would like a copy I will email it to anyone.

 

Desoto1939@aol.com

[Sniper]

8 minutes ago, maok said:

The thing is, your use of the power equation (P=VA) is misused.

 

The power (watts) is higher with a 12v battery than a 6 volt battery because the 12v battery causes the engine to spin faster.

 

And yet my 4 ga cables work just fine.

[maok]

1 minute ago, Sniper said:

 

And yet my 4 ga cables work just fine.

 

Yes, it would, and will work fine with 2 ga, 0 ga, 00 ga but with less voltage drop.

[JBNeal]

additional information - 6 volt battery cable sizing