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!
