# OT: Automotive type jumper cables

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
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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

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On 6 May 2005 19:39:47 GMT, the renowned Ignoramus29781

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
--
"it's the network..." "The Journey is the reward"
snipped-for-privacy@interlog.com Info for manufacturers: http://www.trexon.com
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On Fri, 06 May 2005 16:03:19 -0400, Spehro Pefhany

Thanks for correcting me...
i
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Ignoramus29781 wrote:

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

--
Martin Eastburn
@ home at Lion's Lair with our computer lionslair at consolidated dot net
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On Fri, 06 May 2005 22:09:21 -0500, "lionslair at consolidated dot net" <"lionslair at consolidated dot net"> wrote:

Basically, 4/0 is 4/0.
I had a set of remote booster sockets mounted on my '76 Ramcharger service truck, solenoid controlled, and a set of 25 foot booster cables that plugged into it to start vehicles while in their garage or driveway.
Connect cables to "dead " vehicle, turn on the remote cable solenoid, and let it sit connected for about 3 minutes, and it would start virtually anything. (truck had the big 150? amp alternator to run the hydralift for the snow plow.)

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On Fri, 06 May 2005 19:21:14 GMT, the renowned "Chief McGee"

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
--
"it's the network..." "The Journey is the reward"
snipped-for-privacy@interlog.com Info for manufacturers: http://www.trexon.com
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mount a battery box on the trailer, and charge it occasionally?
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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
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Loren Amelang wrote:

You did. :-)

That only applies if the strands are insulated from each other - so called Litz wire.

I'd be reluctant to trust that at high currents.
Ted
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wrote:

Can be done, Loren - but then you have a MINIMUM of 4 connections on the ground that can (and will) go bad. Much better to reduce that number as much as possible - particularly where copper and steel join. If using frame ground, make sure to assemble with No-Korode or simmilar.
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On Sun, 08 May 2005 19:36:02 -0400, snipped-for-privacy@sny.der.on.ca wrote:

...
I haven't seen any discussion of how the added cables get connected to the battery, whether or not the negative goes via the frame. Personally, I'd make a new negative battery cable from the battery terminal to frame ground, and go from there to the starter ground.
But for the positive... I've seen adapters that turn a battery post into two battery posts - that doesn't seem attractive, space-wise or corrosion wise. Maybe a battery post to bolt adapter, and ring terminals on both the truck starter and booster cable? A Y-splice of cable to cable? Is there some obvious solution I haven't seen?
Loren
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wrote:

A "universal" battery - with side posta and top posts. Use 'em both!!
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Chief McGee wrote:

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:
http://www.bnoack.com/index.html?http&&&www.bnoack.com/data/wire-resistance.html
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.)
--
Jeffry Wisnia

(W1BSV + Brass Rat '57 EE)
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On Fri, 06 May 2005 16:02:47 -0400, Jeff Wisnia

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

But what a unique way to do it!
Jeff
--
Jeffry Wisnia

(W1BSV + Brass Rat '57 EE)
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Jeff Wisnia wrote:

Correct.
I don't know what current it takes to start a backhoe but I lived in Edmonton, Alberta for seven years in the 60's. We had an elderly Cadillac and no block heater. I didn't want to bother installing a block heater since no power was available where I usually parked. I lucked out on a real deal on a 12V set of 60Ah sintered plate vented cell NiCds for cheap. I installed them in the trunk of the car with two 00 (2/0) superflex welding cable (because I could scrounge it) between the NiCds and the regular battery terminals. The coldest I ever started that car at after it had sat for some time was -53F (yes, that is a minus sign). No problem.
Ted
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Chief, I don't own a setup like this, but I have seen them in action: http://www.napaonline.com/cgi-bin/ncommerce3/ExecMacro/NAPAonline/search_results_product_detail.d2w/report?prrfnbr 625772&prmenbrX06&usrcommgrpidWhen you need a boost, just plug into the receptacle at the back of the truck and you are ready to go. Jim
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I think the hot set-up would be something like the quick connect system at the bottom of this page: http://www.painlessperformance.com/webcatalog/cat-battacc.htm You wire in the receptacle at the back of the truck... then just plug in the jumper cables when you need them. David

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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) http://www.powerwerx.com/category.asp?CtgID579 They 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

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