OT: Automotive type jumper cables

In my opinion, it will be cheaper and easier to simply carry the battery back to the backhoe, when needed. It is not any more difficult than screwing around with two heavy gauge cables.

voltage drop = total length of cable * amps *resistance per linear ft

say amps = 200 according to my table, resistance of 4 gauge per linear ft = 0.2485/1000 =

0.00025 feet = 70 (count both ways, to the trailer and back)

voltage drop = 70 *200 * 0.00025 = 3.5 volts.

So, instead of 12 starting volts, you will have only 8.5 volts. Not good.

i

No, 4/0 has the same cross-section as a 0.46" diameter rod, regardless of stranding. So if both are copper, both will act the same electrically in this case. The crimp connections might be a bit better or worse one way or the other, depending.

Best regards, Spehro Pefhany

mount a battery box on the trailer, and charge it occasionally?

AFAIK the electrical resistance of solid and stranded wires of the same gauge is close enough to be identical.

I think 4/0 copper may be a bit of an overkill for your application and you could probably move up to 1/0 without suffering too much voltage drop at say 200 amps cranking current.

4/0 gauge cable has a resistance of .000049 ohms per foot, so even if you use a total of 40 feet out and back, at say 200 amps cold cranking current the voltage drop in the cables would be less than 0.4 volt. You could easily afford to 1/0 cable and still get less than a volt of drop at 200 amps.

A handy wire table for large conductors is at:

That page appears to be for those car audio nuts who absolutely positively have to have kilowatts of ear splitting sound in their cars.

But, maybe you could cut down on the wire cost by using the truck chassis as one of the two conductors? Depends on the layout, but worth looking at, huh?

Jeff (Who remembers when the only "grounds" on vehicles were made to the chassis and sheet metal parts.)

4/0 is a short form for 0000 not AWG 4 (0.048 ohms per 1000 feet vs. 0.24 ohms per 1000 feet).

Best regards, Spehro Pefhany

Thanks for correcting me...

i

Chief, I don't own a setup like this, but I have seen them in action:

you need a boost, just plug into the receptacle at the back of the truck and you are ready to go. Jim

I think the hot set-up would be something like the quick connect system at the bottom of this page:

You wire in the receptacle at the back of the truck... then just plug in the jumper cables when you need them. David

And you could burn out a set of driveshaft universal joints if the grounding strap from engine block to chasis came adrift.

Biggest soruce of voltage drop is at the connectors, crimps, etc. More than likely your gain from running the heavy cable on the trailer would be negated by the extra connection.

Chief McGee wrote:

4/0 copper is 4/0 copper. Many fine wires or few thick wires makes no difference to the current capacity. So, you might as well use welding cable, unless you have one on hand for free and the other is a need to buy item.

You may not need to go to such heavy cable if the backhoe battery is basically OK. What you can get away with for topping up and recharging a good battery .vs. what you need to have a hope of actually cranking via the jumpers is quite different. A couple of 10 or 12 gauge wires hooked in to trickle-charge the backhoe while you were hauling it might be all you need.

Just out of curiosity, how does that haul, and how much backhoe have you got? I've got a ~7-8000 lb backhoe which I don't haul anywhere, and a

1-ton crew-cab pickup. I've always suspected that if I did decide to get a trailer that could take the hoe, it would be the tail that wagged the dog on that truck (about 6000 lbs empty and 20 feet long).

-snip-

I used to drive a truck for my dad's company in the summers. It was a

1972 3/4-ton truck pulling a 20-foot gooseneck trailer. We ran it up to 16000 pounds combined GVW and it towed just fine. With the gooseneck putting the weight ahead of the rear axle it basically towed like a semi (so I've concluded, that truck was the biggest I've ever driven). There was no sign of the trailer wanting to whip or jacknife, the combination handled nicely around corners, etc., etc. The ride was considerably rougher, and of course the thing neither accelerated or pulled up hills with any speed (we were running a 350 with a 4-speed), but there were no _handling_ problems at all.

Of course it beat the hell out of the pickup, but Father has replaced the bed floor and all of the rivets in the chassis -- it's fine now.

How about building a charging system to keep the backhoe's battery at full charge and an inverter to keep the engine warm via a block heater. Make sure to use a diaode to protect the truck's alternator and battery. Hope this helps..

But what a unique way to do it!

Jeff

"Chief McGee" wrote in message news:KsPee.53112$NU4.36168@attbi_s22... | I pull a backhoe on a trailer behind a 1-ton GMC truck. Sometimes when it | is cold I need to "jump off" the backhoe from the truck's two batteries | while it is loaded on the trailer. Since the jumper cables are too short to | reach the tractor from the front of the truck, I would like to run two | permanent cables to the back bumper of the truck . Then I could hook | regular jumper cables from the tractor to the terminals on the back bumper. | Question is: What type and size cable should I run? Would 4/0 copper | "entrance" cable do? This is stiffer than welding leads, therefore, harder | to work with. But if it gives me more cranking amps it would be worth the | trouble. Does a 4/0 copper with a few thick strands carry more CRANKING | amps then a 4/0 with many finer strands? Thanks, Chief

Most RV's have a setup that allows the main battery to charge the RV batteries as you're driving around. Check with an RV shop about upgrading your wiring connection point and making a suitable connection to the tractor. If you'd rather go the jump start routing, Anderson mutipole connectors are used all over for battery cable connections on heavy equipment and battery powered equipment like forklifts and such. If I ever was to hook up a set of jumper cables into my crew cab, I'd use a set of these. If you look at cop cars and whatnot you'll see them hanging out the front and/or the back.

and you can get them from many sources. Battery shops, better auto parts stores, RV shops, and heavy equipment suppliers.

Here are the connectors you want to use (took me a while to find them when I was looking some time ago -- Anderson makes them)

are really cool - they are polarized, but both sides are the same and the "fingers" overlap when you plug them together. Really slick - you can have a connector on the battery, one on the Jumper cable and one on a cable from another battery and plug them together in any combination and + goes to + and - goes to - every time. Same type of connectors they use for the big batteries on the electric fork lifts etc. Places like Interstate Batteries carries them as well as many others. The "fingers" recessed so there is never a terminal stuck out. Good for 350 amps for the ones on the link. (they come in various sizes)

mikey

in

Naturally that is at 200 amps. Not the normal current needed at all.

Also, if one simply hooks one up, the batteries will float at what ever current it took to bring up the flat one. With the good one running a generator, simply charge up the first for a few minutes, then the voltage drop will be much lower.

I don't jump cars. I charge a battery, disconnect and let the other start their car. If not up yet, charge until almost charged and then allow cables to stay on as boosters. The main battery being charged now starts the car without blowing the 'diodes' in the alternator.

Martin

Last time I was in one of my "secret sources" they had a bin full of electric forklift charging plugs, male/female inlines. I could be persuaded to go pick up a couple sets

Gunner

"War is an ugly thing, but not the ugliest of things. The decayed and degraded state of moral and patriotic feeling which thinks that nothing is worth war is much worse. The person who has nothing for which he is willing to fight, nothing which is more important than his own personal safety, is a miserable creature and has no chance of being free unless made and kept so by the exertions of better men than himself."

- John Stewart Mill

I didn't see anyone answer the "question" (maybe I missed it). If you are carrying high frequency AC (like radio signals), the current clings to the outside "skin" of each strand so more are better for current carrying capacity. Otherwise wire size is wire size - more strands are just nicer to work with.

You may not need two cables front to back. The battery negative is grounded at least to the truck starter, and in some fashion to the truck frame. It would be good to verify how heavy a conductor was used, and maybe provide a new heavier frame ground in front. Then just run the positive back, and pick up the ground from the frame.

Loren