Can someone please help me settle a debate with some colleges? I don't work on highway tractors, but I was asked to take a look at a CAT C15 that won't crank over in the cold under 20f and is very slow to turn over even around 50f. I took some voltage drop measurements on the cables going from the battery to the starter and recommended replacing the cables and the battery interconnects. The truck has had 3 starters replaced in the past 2 or so years, not sure why. I connected a Picoscope to measure the voltage drop on the cables and the cranking current and this is what I found. The cables are about 8ft long and go directly from the 4 group 31 950CCA amp batteries in 12v parallel to the starter, and then the frame is grounded off the starter lug. Because of the length I recommended 4/0 welding wire with sealed crimp terminals. I also recommended connecting the ground at battery 1 and the positive at battery 4 instead of connecting both cables to the first battery. I am getting a lot of push back and told I have no idea what I am talking about, that 2/0 wire is overkill and 4/0 is just stupid.
Calling @Simon C - you're up........... My thought FWIW is that for a 12V system as opposed to a 24V one is that losses in the cables are doubly important which is why a larger cross-section of cable makes perfect sense. I still fail to understand why US trucks still use 12V systems when the rest of the world switched to 24V somewhere in the middle of the last century.
Okay so I have figured out lots in the cold and I looked at the amps draw and voltage loss and here is what I think: New Detroit Diesel DD16 engines come with 3/0 or bigger, seem to have seen one with 4/0 on one. Remember a long time ago all the trucks were starting on a series parrallel switch and 24 volts to start the engine. On big Cat Dozers still all 24 Volt. Problem is that on 12 Volt new trucks the cable has to be huge to not lose as much voltage force when cranking. Add to that cooler temperatures and the need for PROHEATS to get the engine up to tempeerature and you need 4 batteries as Bullitt has posted for a good reason. With all the newest gadgets on these trucks and the fact that all cables will decompose in time 4/0 cables and ends would be better versus inferior. People forget that at 0F or minus 18 C a battery that is perfect in integrity only has maximum 30% of its cranking capacity. I have redone some trucks with 3/0 cable and a lot of problems disappeared. I have many a time installed a second cable from the alternator output post to the positive of the starter or to the positive output of the batteries. Better to have the ground in the middle of 2 battery sets and the Positive in the middle of 2 battery sets to get more uniform charging of batteries. Hooked up on the ends will leave some deficient. Simon C
Seen a picture somewhere on the internet where a guy took the 4 battery positive posts and sent them to one long copper buss bar. He sent the 4 battery negative posts and sent them to one long copper buss bar. The Positive buss bar went to the starter solenoid and the Negative buss bar went to the frame or Starter ground connection. This setup guarantees more even charging. Simon C
Last thing to mention is that poor batteries love to kill starters cause they don't have the power to make it crank fast so it just cranks half speed for too long and overheats the solenoid contacts and need new starter. Good batteries with good cables mean high speed of crank which makes cylinders get hot fast and fire. Once firing on one or two there is way less load until starter bendix retracts. Simon C
Freightliner for example uses 3/0 cable, ground at starter to frame/engine block and ground at batteries to frame. Now to above post, 2007--that's a old truck one of the last to get a Cat. So with that said, I would be willing to bet the cable lugs have been heated who knows how many times and built a layer of char inside the lugs, same with battery crossovers. * IMO--minimum of 3/0 all new lugs and crossovers with added grounds.
Obviously, you have the data proving your point. The ATA and the TMC recommend no more than .5 volts drop from bat to starter. And, same for the ground side. The manufacturers have been going cheap on the copper for a long time. Like Truck Shop said, those lugs get worse everytime they are overheated. One of these days, the solenoid contacts will eventually weld themselves and She’ll burn to the ground.
That truck--19 years old--starters are probably 4 including the original equipment from new. Most of the time a lug can be cut open and blackened copper is found. Batteries are replaced, starters replaced and cables will stay because of the pain to replace. With all the dead engines from all sorts of issues including priming cables get a workout from extended crank time.
How well does the insulation on welding cables hold up to being in contact with fuel or oil? I've never actually ran heavy gauge welding cable to a starter before.
Very well if it has neoprene insulation. EPDM, not so much.
Proper voltage makes magic stuff happen inside a starter to limit the amperage draw. When the voltage is low the magic stuff can't happen so there is no limit on the amperage draw. That unlimited amperage draw is what welds contacts.
Until the starter it's self is the problem. With newer trucks parasitic draw can kill a 4 battery system in just 12 days of setting, and if that repeats many times the batteries are prematurely toasted. We've had brand new trucks set waiting for permits/license for two weeks and if not started every so many days batteries are extremely low voltage. Average starter life is around 3.5 to 4.5 years, batteries 3 years at most with constant draw/recharge rates. The old MT series were the ones to weld contacts, newer gear reduction never had that happen. But trucks are equipped with start stop these days so the entire system gets a work out.
That is a good question, my opinion which ain't worth much is that welding cable is not as good as true battery cable because battery cable has a neoprene cover as Coaldust said. Them cables can take oil and fuel like nothing. Welding cable the skin will get soft eventually. I have supplied welding cable often cause I can get it for 1/2 the price of battery cable for machines or trucks that are close to last legs, and owners think their blackened copper cables are still good. I always put the cable in split loom which is in bags of 50 feet to help protect. Simon C
Petes from factory either run 2 4/0 cables or 4 2/0 cables. I find the 2 4/0 cable setups better and less cluttered in the battery box. Another thing to mention is the factory rubber boots around the cable ends are supposed to have a copper washer on top if the cables are stacked. Lots of times the cables get stacked backwards resulting in a rubber/rubber connection instead.
And many times a 5/16" steel flat washer is found.
As for cable degradation, anyone whom has burned some rod, a lot of rod, knows how important it is to periodically cut back the cables because of the burning. Welding typically makes good ground after rod strike and even still, if welding for a while, the heat builds up and the stinger and cable will get hot. I use 2/0 lightweight for a 12’ whip but my regular leads are 4/0 along with my extensions.
Hard to find copper washers around here, so for most applications I use Zinc plated grade 8 washers and spray them with Lloyds moovit or Deep Creep penetrating oil afterwards, and they come apart looking good 1-2 years later. Sometimes the best is not available. Your suggestion is a good one though. Simon C
Those would be good cables, glad I don't have to carry 100 feet of them. Simon C
I certainly didn’t make them, came from a retired welder and that’s the reason for the lightweight stinger. Was ruining my shoulder but what else do you do with them? Worth too much to scrap. Does come in handy when doing a lot of carbon arcing.
Might be lucky in that respect, the local farm/garden/hardware store on my end of town has a vast selection of specialty items other than the standard nut/bolt selection. Washers of every type/material/grade.
I try and use injector washers, unless I have star washers, dammit forgot to order more star washers. lol
It's easy to make copper washers out of old copper pipe. No reason they have to be perfectly round.
I have never been that hard up or desperate yet, but a depression is around the corner so I'll keep that in mind.
I just pulled the battery cables on my 379 Peterbilt with a 3406E. Battery box 5 feet behind the cab, so I would say the cables are 12 feet long, there are 2 positive 4/0 cables and 2 negative 4/0 Cables, with 4 batteries. I verified with a second Peterbilt 379 3406E truck that has the same setup. Because the there was a Prentice Log loader behind the cab, hydraulic oil leaked on the cables and broke down the outer rubber and the cables became a an open corroded mess.
So that is a very old truck ( 3406E ) and some have been redone with welding cable as I have done, but real battery cable will last longer in the hostile work world of water and oils . Copper is pretty steep priced these days, but so is a new truck, never mind the problems they are having. New cables and ends and you will be good for a few years. Simon C
Battery and cable MX is a thing. But, ain’t nobody got time for that.
Can see an extension cord going underneath. Many a cord has burn't down machinery amongst other things. Simon C
I’ve never seen a 15 amp block heater cord catch a rig on fire. The breaker trips or the cord shorts and then opens. The orange end of the cord melts. It looks ugly, but never catches anything on fire. Not, saying it won’t happen. I’m heading to the terminal tonight to change a melted cord on a ISX. Well, more like splice a new end on it. One of those $500 PACCAR block heater cords that makes three passes around the engine, heads to the oil pan heater, then the block heater, then to a T-stat before returning to the plug. And takes 6 hours to replace if you follow what the OEM did.
Year 1999, I pulled a 1984 359 with a fresh rebuild I had done six months earlier into the shop. It was winter and decided to plug in the block heater to test. About one minute later I heard this crackling/popping sound then flames erupted. I yanked the cord from gang plug on wall grabbed a extinguisher to kill the fire, It NEVER tripped the breaker. Had I not been there it would have burned the shop to the ground. So before each winter I would unscrew every stinking cord connection from heater probe to check that it hasn't been over heated plus check all cords from block to cab outlet. Only takes once to create a pulse rate of 180 over 120.