The Stovebolt Site Forums The Shop Area The Electrical Bay 4/0 battery cables? Bah Humbug!

Well maybe it’s not Christmas and I maybe some will call me the grunge that spoiled the cable myth. But, I was layin’ awake last night doin’ some thinking’ bout all this talk of monster battery cables. There has been a lot of here say about the bigger the better when it comes to battery cables and how much better the starter will perform.

I’ve just finished rebuilding, complete rebuilding that is, with the coils out and all, a couple of starters for my truck. I couldn’t help but notice that they crank the truck like a 12v system now, well maybe not like a 12v system but durn near as nice. By that I mean that the start is now very crisp, snappy and faster compared to the way it was and the way I’ve seen a lot of other 6v systems perform.

The truck had a new #1 cable and 585 CCA battery installed a couple of years ago, right before I bought it. Hearing that a 2/0 cable would give the starter better performance and that a 4/0 would be even better I picked up a 2/0 cable at Farm & Fleet last visit. As often happens I felt this need to satisfy my curiosity and to test out what I suspected to be, an urban legend. Some thing just didn’t seem logical about the “bigger is better” theory when I compared the cross section of the field coil conductors to the cable gauge bringing the power to them. Bigger IS better, to a certain degree, and this is about what degree you have to take this.

I’m not going to throw out a bunch of numbers here, one only has to look at the cross sections of the conductors in the circuit and apply a little common sense to see that to feed a conductor that has a cross section of .036sq.in. you do not need a cable with a cross section of .300sq.in.

The matter of resistance vs. cable length will no doubt be raised so I have included the resistance of the cable in ohm/1000 feet @ 20°C; 1AWG = .134ohms, 2/0AWG = .084ohms, 4/0AWG = .053ohms. By applying Ohms law one can see that very little voltage will be dropped across any of these cables allowing for virtually all of the voltage to be available at the starter. With a four-foot length it would be impossible to measure the resistance even with the most sophisticated instruments.

The cross section of the stock field coils conductors (2 of them) is .036sq.in. The individual coils are just half of that. This is the reason that Delco-Remy cautions against cranking the starter motor for no more than 30 seconds at a time. A conductor of this size is simply not heavy enough to carry a large current for very long with out over heating.
Now supplying that coil would normally be a #1 battery cable. The illustration shows the cross sections of the copper conductors being considered here. The current ratings for a 100% duty cycle are based on a 5-minute period, which is a standard for the welding industry. How much current will we draw? Some where around 400amps most likely! But even with a 1AWG cable at 450amps we still have 30% duty cycle loading capacity.

Conductor cross-section illustration:
http://rides.webshots.com/photo/2926654400098611668aBdvzM
Field coil conductor vs. #1 battery cable:
http://rides.webshots.com/photo/2799125410098611668OxmYjj
#1 cable next to the 2/0 cable:
http://rides.webshots.com/photo/2144920660098611668WRUsTy
#1 and 2/0 cable routed to battery:
http://rides.webshots.com/photo/2719417800098611668yClCcm
This 2/0 cable will not fit in the space where the clamp normally would hold it, between the floorboard and frame with out prying up on the floorboard. It would be impossible to fit a 4/0 cable in here and it would also be difficult to make some of the bends with a 4/0 cable.

So based on this information I have come to the conclusion that with a properly rebuilt starter and clean connections throughout the circuit, that the #1AWG Belden battery cable that was used in this truck is perfectly capable of starting your Stovebolt under any normal circumstances.
Denny Graham
Sandwich, IL

Boy I sure hope somebody reads this cuz I dun put in a whole bunch of effort to share my findings on this one!

Um...

Uhh...

Do you, um, maybe have, err, just a little to much time on your hands???

Hmmm...

I have 3 times & each time I sat here & thought........


oooooooook........




Denny I know you put a lot of thought into all of this but I have one question for you.....

Does your brain hurt???????...Joe

Denny, I am in agreement with your assessments with a stock battery location and stock components unless you move the battery to the rear and like me have a 200' spool of 4/0 cable and the ends needed to make big battery cables. (We upsized at work from 4/0 to 500MCM and I got to keep the scrapped stuff) Plus I will be running a BBO in my AD. When I make cables for other projects, 2/0 is just fine for most cars with trunk mounted batteries. voltage drop is of concern so battery conductor size is the largest contributer here.

The biggest issue is ground connections and cable connections at the starter. This is generally the source of most peoples issues with the starting circuit (unless you have a bosch starter and the exposed copper conductor to the + side of the winding corrodes off due to road salt - another story)

Scott

denny, I gather ALL information, make a "educated" guess and then go do what I wanted to all along! Thanks for more "insight".

Well Jeff, should I not have shared my research with ya all??? Just a push of a button and I can remove it if ya want and ya can go on believing what ya want.
Nope Joe, the old brain needs exercise just as much as the biceps.

Scott, if ya check out the resistance of 20 foot of 2/0 cable at 12v drawing 200amps your only gonna drop around 336mv in that length and at 6v drawing 400amps about twice that much or 672mv. That leaves the rest to be dropped at the starter. I think this bigger is better thing is being overplayed. It doesn’t make much sense to put a cable that’s 5/8” of copper on a lug that’s only 3/8” which is soldered to Field coils that are about the size of a number 8 or 10 conductor.

Denny Graham
Sandwich, IL

Denny
Thanks for your efforts. Most time I think people just suggest that 4/0 cable because it is a simple (but often incorrect) fix for some other problem. That other problem is sometimes cheaper to fix then replacing with 4/0 cables.

I often find it interesting that people dismiss what the OEM had figured out long ago. That is, what is the most economical solution. They didn't pay those engineers for nothin'!

I've never seen anyone suggest a 4/0 cable (0000) for a 6 volt system. Some might even argue that a 2/00 (00) cable is overkill, although I swear by them (on power lead and all ground leads).

A 4 gauge cable is OK for 12v system. I think 2 gauge or less is recommended for 6v systems.

No Denny, dont delete it. Its useful information. I was just being a smartass, simple as that.

Jeff

Well Tim, ya need to go to VCCA chat and listen to the old timers and experts over there. Several discussions that have been going on there for a while now. In fact that’s what prompted me to dig in to it a little deeper and look at some real numbers. Although I’ve done enough to satisfy my curiosity, someone else might care to do a search on this forum. I’m pretty sure I’ve seen the same suggestions here. I’ve been in and out of welding most of my life, pop started teaching me when I was just a pup, and a four/ought cable is even a biggie for welding cable.
Nope Jeff, I taint gonna pull it, ya smart [censored]! (just kiddn’ ya buddy) This subject comes up often and when it does there is usually a lot of misinformation that comes from it. like I said, I just wanted to get the facts out on the table.
I don’t think you can stress too much the importance of having clean connections to insure top performance of the electrical system. That probably contributes to the vast majority of the electrical problems that we encounter.
Denny Graham
Sandwich, IL

Hmmmm! :/

Stuart

Gosh, Denny, I thought the people over at the VCCA site were only interested in original equipment.

OK Stu, I rewrote that line for ya, I hadn't had my cup O' joe yet so guess I was still half asleep.
Ya know Tim, so thought I, but apparently they allow for some exceptions. If I keep causing trouble for the founding fathers they just might ban me from posting and quit sending me the G&D!
Denny G

OK, let me go drink at least two 6-packs, to prepare for the whizzing contest!

I prefer to deal with real-world experiences, rather than delve into mind-numbing theoretical discussions. A piece of #1 or #0 welder cable, with its hundreds of hair-fine strands will provide all the current-carrying capacity any 6 volt starter will ever need. As long as the terminal ends are soldered on for minimal voltage drop, and kept tight, there should be absolutely no need for mega-cables.

The practical way to evaluate a starting system's performance is a "series resistance test" where the voltage drop is monitored at each cable and connection from the battery to the starter, and back to the battery while cranking is in process. On the hot side, the allowable voltage drop on a 6V system is 0.1 volt per connection point and ZERO voltage drop from one end of the cable to the other. Ditto on the ground side. 12 volt systems can tolerate twice the drop at connections,(0.2V) still with little or no drop from one end of a conductor to the other.

I ran an 8D series 12 volt battery that weighed over 120 pounds in my road service truck, with 2-0 welder cable run to both ends of the truck to plug-in booster cable connectors, with the same type of cable in 25-foot lengths to my jumper cable clamps, and boosted Cummins, Cat, and Detroit engines with them with no problems. I also had a 200-amp brushless alternator on the service rig. 4-0 cables- - - - they're totally unnecessary, even for jump-starting a bulldozer!
Jerry

Cripes Jerry, that's what the whole point of this thread was about. Did I do that bad of a job trying explaining my findings? I was just trying to dispel the myth being spread around that using these big cables improve the performance of the starter and tried to make the findings as simple as possible. All one needs to understand what I posted
is E=IxR.
My finings were that there is No, None, Nota reason to use 4/0 or 2/0 cable? In fact a #1 is more than adequate for a stock Advance Design Truck or most other 6v trucks or autos even if the battery is mounted in the trunk.
Denny Graham
Sandwich, IL

I'd had my starter rebuilt and had 2/0 cables put on... Before the rebuild the starter lagged now it works great...that all the research I needed...Peter

The starter lagging or cranking the engine over slowly very well could have been because the starter needed a rebuild. Assuming that no wires are burned up in the starter about all there is to it is a commutator and a set of brushes. Unless the starter has a life time of starts and stops on it, like in a package delivery situation the brushes probably aren’t really worn down completely, remembering that unlike the generator the starter only turns over a few times every time you drive it. So in reality assuming all of your connections from the battery are solid you can usually narrow a weak starter down to a problem at the commutator. If the commutator is not worn but just oxidized or covered with burned oil a good cleaning and sanding/stoning will generally bring the performance back to normal.
Just changing out the cable generally gives a fresh clean path for the current at the connections. Again, my point is, if you have a properly rebuilt starter motor, and a good solid #1 or even #2 cable and CLEAN connections your 6v starter is going to perform up to par. No need for monster sized battery cables.
I think the myth about better performance after changing to a 2/0 or 4/0 cable is due to the fact that in the process of changing the cable they re-established a good lo-resistance connection. As Jerry brought up, the connection at the lugs needs to be solid, if the lug is simply crimped then moisture gets into the joint and you loose continuity between the lug and the copper wires due to corrosion. This creates resistance at the joint and you begin to see a voltage drop at this point. The more voltage dropped across the connections the less available to the starter and the slower it will crank. Again, as Jerry points out a soldered lug is definitely going to give you better performance over a longer span than simply crimping the lug.
Denny Graham
Sandwich, IL

HI Denny,

Thanks for the post. I don't know the theory of electricity as well as you and Hotrod Lincoln but I sure do respect your electrical knowledge, defined research and sharing that information. Now I am a bit confussed.

I have always thought that electricity is like a garden hose. A large diameter hose is able to deliver a greater volume of water compared to a smaller one and electricity works the same way. most starters require 200 amps or less to crank over an engine. most batteries are 800 cold cranking amps. the weak link is "usually" the cables, which are unable to deliver those 800 amps to the starter. Of course I always soldered my lugs as you mention and the system clean for top performance. I was under the impression that this is why a 12 volt conversion works so well on a 6 volt system. Its like having lots of pressure and a fire hose. Six volt systems do not have much pressure behind the amps so a physically bigger wire was used to deliver "volume" needed to make the accessories work...As always the knowledge here is amasing...Is this incorrect?

Dave

Now my brain hurts... :hammering:
I have only one observation. I know from many years of experience that heavy duty ($$$) jumper cables will start a vehicle when those light duty (cheapies) won't. Does that relate to this discussion or is it a side issue?

Sounds like its related to me and my brain hurts also,,,lol.

BIG CHEVY 3600,

Yes, the gauge of set of jumper cables will determine if they might be useful when starting a 6v vehicle. Heavy duty jumper cables cost more because of the much heavier gauge wires (and clamps).

Yes, your observations directly relate to this discussion. Denny's study relates to jumper cables, too - size matters, up to a point (some us would say that 2/0 is that point and no one seems to be arguing in favor of a larger gauge).

Tim

Dave, the speed of a motor is determined by the voltage applied to it. That’s why your 12v system cranks the engine over faster. Your reference to the garden hose relationship is used as a simple explanation of the relationships of pressure to the current flow thru a restriction. In an actual electrical circuit heat dissipation plays a very important part. Normally when you heat a conductor the resistance goes up unless it can dissipate the heat at the same rate it is generated, This is where the 100% duty cycle becomes important. If you like the water analogy, think of a bucket with a hole in it, the hole where it comes in has to be the same size as the one that goes out or it overflows. In a series circuit the voltage is divided proportionally between the individual resistances. The major components here are the starter, the cable and the battery. If any one of them is over heated the resistance increases in sort of a snowball effect, or chain reaction, i.e., more heat/more resistance/more resistance/more heat and on. What you have to keep in mind is initially your going to hit the starter with the full current and voltage available, and if the cable is undersized it will begin to heat up and require more of the voltage to push the current thru the now increasing resistance. If your really interested in more on your gonna need to start digging into it your self. Ya might start at sites like this; http://www.stealth316.com/2-wire-resistance.htm
I’ve put way to much time in it already and am about burned out myself. I’m neither an electrical engineer nor a terribly good electronics technician; I am a fairly good mechanic though and I was just tryin’ to apply some common sense to the subject.

Jim, like Jerry said earlier, I’m not aiming to get into a whizzin’ contest with anybody here, and I’m not trying to offend you, but I would have to disagree with you on the jumpers. In my opinion, unless the smaller jumpers were drastically undersized they would initially deliver the same current. Most engines start after a few revolutions or within a few seconds. If the jumpers would not start the vehicle it was most likely because an excessively long period of cranking and they were getting hot, i.e., the resistance was increasing and the voltage available at the starter was now being dropped in the cable.
And once again I have to refer back to what the Delco-Service bulletins caution, “Never operate the cranking motor more than 30 seconds at a time without pausing for a few minutes to allow the cranking motor to cool.” The same thing applies to the cables, unless you have a cable large enough to handle 400plus amps at a 100% duty cycle.
Fin;
Denny Graham
Sandwich, IL

Not to hijack this thread but Denny speaks of heat and resistance and my question is, do I need to sheild my starter from the exhaust on a 350?
http://good-times.webshots.com/photo/2374147040099708909RtRbDt

BTW Denny, you couldn't offend me if you tried. I am constantly amazed at your focus in your restoration process. It is apparent that you're retired and for that I am jealous. I have more than 75 employees in my three businesses and they are all women, twenty or so drive the 11 vehicles the companies use, half of them are school buses. Now think about this, 20 women trying to start vehicles that are not close to being new; how many times a year do you think I have to use those jumper cables. I can bet money if the battery is way low the cheap cables won't do the job. I carry welders’ cables for jumpers and most times they are the ones that get the job done. Parenthetically, understanding the monthly cycle of women and with 75 of them, it is not unreasonable to assume every day will be tough for several, and that should give you a great deal of sympathy for me.

Good deal Big guy, what ever works for ya. If I were using jumpers that often I would probably be using welding cable to.
Sounds like you got 75 headaches to wake up to every day. Whatca gonna do with all that money Jim?? Don’t stay in the game to long, ya might not get to spend it.
Yep, this here retirement thing is about as cool as anything I've ever done. I wish I could have done it sooner. I started to notice all my buddy’s wife’s were becoming widows in my late 50's and figured I orta get out as soon as I could. Finally called it quits bout three years ago, at 63.
Denny Graham
Sandwich, IL

55 here lol its great...Peter

That puts you 1 year older than me Denny and a lot smarter. My son is a Jr. at A&M and will take over things and send me checks if he ever grads. We have a farm down in the hill country of central TX and I'm building a 30X40 garage (get away) for my projects. Hope I live long enough to enjoy it.

Hay Denny
I for one appreciate it... Thanks a Bunch, you're doing a great job and service by helping many many more that do not write in this thread.
Others will view this many years from now and will follow your efforts. I like this site because many restoration guys (and gals) do some mighty fine work on these old trucks, that we love to tinker with (& my motocycles also) and they inform us when and have answers about specific projects they completed.
keep up the great work everyone and we can always do w/ some ribbin'
&& those eating kind too.

Denny,

Thanks for the information and the site. By the way I retired a few years ago at 51. It's been the single best thing I done in my life and now with plenty of time to read, I will research the subject...again , thanks for the site.

Dave

Denny
Thanks for the insight to this bigger is better thing which I wondered about. I understand what your saying, but then its easy for me cause I was an electrician when I was younger.
Hey is the Sandwich Fair still great, I used to go every year when I lived up that way before moving to Missouri. It was the best fair to go to.
Dan

Great Fair, still the best in the state of Illinois. I live at the airport just a couple of blocks south of the fairgrounds and always try to take a day for a walk through. This year I think I might take the pickup over for the car show.
Denny Graham
Sandwich, IL

From experience I like 2/0 cables, even for 12 volts. They may be extra big, but they are still easy to work with and install, and do a great job.

It's also a great idea to run your battery ground cable directly to a mounting bolt on the starter, many times that solves a slow cranking problem. Most diesel engine starters have a ground post on the starter for connecting the battery cable to.

Another consideration is what happens when strands start breaking or corroding inside the cable, then bigger is better, as it will last longer.

When soldering cable ends on I like to use the heat-shrink stuff with the glue inside to help seal the cable ends from corrosion.

Another thing many people don't understand is how terrible those quick clamp on battery ends are, the ones with the sheet metal strap and two bolts that sandwich the cable to the clamp. given a little time they turn into really bad connections.

Another important tip, don't use acid core solder, or acid as a flux, when soldering electrical connections.

Grigg

Denny,
I find the #1 works just fine on my truck. I did notice when I first started to mess with the truck as found, that with the 6 v starter, losing some voltage in the cables and connections really affects the cranking ability.

Well Fred, I'm bout talked out on this on, but I just don't find that problem with mine. And the numbers that I come up with just don't bear that out either, voltage drop in a 39" long #1 cable is minimal and if all is right ya shouldn't see more than a couple hundred mv. Once all the electrical was cleaned up, replaced or rebuilt, she cranks over plenty fast even in this cold weather. I'm parking it in the garage so it's not sitting out in the cold but the garage is down to just above freezing.
Denny Graham
Sandwich, IL

Resin core solder for copper.

Just as a quick note, in the automotive and truck field (by the books I learned from) 12 volt electrical circuits are allowed .5V total voltage drop on the positive side (for neg. ground systems) and .2V total voltage drop on the ground side. If under cranking conditions, you are within these specs, your cable size is fine. These specs have guided me without fail professionally. Thought I would add what I know.

Well, I missed the whole thing from the beginning, but I use 4/0 cable for the simple reason that I keep 4/0 on hand for my trucks and no one in town has 2/0. I thread it through to the original battery box with a group 1 battery. I know its overkill, but its just a matter of convenience.

Denny,

Well said, and I agree with your findings and your conclusion that "bigger is better" has its limitation as universal advice.

Harvester

Why does it say in the Tech Tips that 4 Gauge battery wires are correct for a stock 6v application? The battery grounding cable was hanging on by a thread at the terminal. I replaced it with a 4 gauge wire from the parts store and haven't had any problems. I checked several websites regarding battery cables for a 1946 application and most major brands say 4 gauge with the exception being Autozones website which stated 2 gauge in which I can't find. They don't even carry 2 gauge inside the stores.

Over 50+ years of maintaining high-current starting systems, I have learned that within reason, bigger is better. Another consideration is not only the cross-sectional area of the wire, but the number of strands. The hair-fine strands of welding cable will carry far more current, with less voltage drop, than regular battery cables will. Current tends to flow along the surface of strand of wire, so 500 strands will carry more current than a 50-strand cable with the same diameter.
Jerry