Automobile 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? Is welding lead the best wire to make jumper cables? What size? Thanks, Chief
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At DC, I don't think there is a measureable difference between the two cable types. They make heavy guage cables with large plugs on them for winch applications. This is so you can use one winch on your vehicle by moving it from the front to the back. I would look at that type of cable and then add a compatible plug to the end of a set of jumper cables.
Charles Perry P.E.
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to
bumper.
harder
I know that back hoes can be a bit hard to start on cold mornings. I challenge you that 4/0 is needed. I would think that #4 maybe less sized conductors would be all that you would need.
Your might consider a inverter and a battery warmer. Smaller wire for sure. You would need less than 1500 watts. http://www.kimhotstart.com/products/battery_heaters.htm
The biggest concern would be the routing and protection of the cable from the front to the back of your truck.
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AWG is a standard that relates to current carrying capacity of the wire. See: http://www.powerstream.com/Wire_Size.htm All current values are for continous draw. The calculator at the bottom can be used to determine the voltage at the backhoe batteries (the box labeled "voltage at load end of circuit"). Welding wire is usually the cheapest solution.
Dwayne
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Here's how I'd go about solving this...
First, make sure the charging system on the backhoe is in good order. It may not be keeping the battery fully charged. Make sure the top and case of the battery is clean. You might also see if there is a key-off drain on the backhoe battery. If there is, find it and fix it, or install a battery cutoff switch in the negative cable of the backhoe battery. After you drive the backhoe up onto the trailer and shut it down, flip the cutoff switch and your battery is guaranteed to be disconnected from everything on the backhoe so it won't discharge. Just remember to flip the switch again before you fire it up.
Second, if the backhoe battery is fully charged and it's still hard to start (old engine, it's cold out, etc), you might try warming up the battery, as has been suggested. You can test this theory with a plain old drop light / trouble light. Some morning when you don't have to go anywhere, put the light near the battery (under is best) on the backhoe and leave it plugged in for an hour or so. Then try starting the backhoe. If it starts up, you can either warm up the battery before you leave the house, or install a heater on the backhoe. There are battery heaters available that work off of 120 V, but then you need an inverter to get the 120 V. If you have a long enough drive from the house to the job, or can go out and plug in a connector some time before you leave, you might install a 12 V heater on the backhoe.
Buy a couple of double-contact automotive bulb sockets and mount them under the battery on the backhoe such that the shells are grounded to the frame. Put an 1157 (35 W) or 2357 (37 W) bulb in each socket. Wire all four wires together and to a piece of 14 gauge or better wire. Also connect a piece of 14 gauge or better wire to the backhoe frame. Run these wires to a 2-wire connector on some handy place on the outside of the backhoe. Run two more 14 gauge wires from the trailer connector to the mating 2-wire connector. At the trailer connector, connect the hot wire to a separate contact - don't hook it to the running lights as the new bulbs probably draw too much for the running light circuit. Hooking the ground wire to the existing ground wire in the trailer connector is probably OK, as long as you upgrade the ground wire on the truck side of the connector to at least 14 gauge as well. On the truck side, run a 14 gauge hot wire from the new contact to the battery, and put in a 15 A fuse at the battery. Now, whenever the trailer connector and the 2-wire connector are both plugged in, the backhoe battery is getting heated. You probably don't want to leave this plugged in overnight as it would drain the truck battery too much. But plugging it in an hour or two before you leave should be fine.
Third, running permanent cables is also a valid option. Tow trucks often have cables that come in two parts. There is a short part (three or four feet long) with lugs on the ends of the cables for attaching to the battery. The other end has a two-pole "Anderson" high-current DC connector, which gets mounted to the truck grille. The long part of the cable (ten feet or more) has jumper clamps on one end and the mating Anderson connector on the other end. The only problem with this scheme is that the short end of the cable is probably too short to reach the back of your truck.
Welding cable is probably a better choice than entrance cable, since it's more flexible and therefore better able to withstand the vibration of an automotive application.
What I'd do is to buy a chunk of #2 or #4 welding cable a little bit longer than the truck, some copper lugs to suit that cable, an Anderson connector and the terminals for it, a length of split corrugated tubing as long as the welding cable, a set of jumper cables long enough to go from the bumper of the truck to the backhoe, and some miscellaneous zip ties, mounting screws, etc.
First, cut the clamps off of one end of the jumper cables, and put the Anderson connector terminals on the cables. You can solder them on (use rosin-core solder and a propane torch; they're too big for a soldering iron) or crimp them on - trade beer (or whatever) for use of the crimp tool with an electrician friend, or possibly rent one.
Next, figure out where on the bumper you're going to mount the other Anderson connector, and cut a piece of welding cable long enough to go from there to one of the frame rails on the truck. Put the Anderson terminal on one end and a lug on the other end. Put the corrugated tubing over the cable. Use an existing hole in the frame or drill a new one. Use sandpaper to get the area around the hole down to bare metal, then bolt the lug to the frame. Use a lock washer or Nylock nut on the other side - don't use a sheet metal screw or lag screw. Spray-paint the completed connection to cover up any remaining bare metal. Plug the terminal into the Anderson connector and bolt the Anderson connector to the bumper. Use the zip ties to dress the wire up out of the way.
Up front, locate another hole in the frame rail near the battery, and prepare it the same way (bare metal). Install a cable from here to the negative terminal of the battery - you can either make one out of lugs and welding cable, or buy a ready-made "switch to starter" cable at the auto parts store. (Yes, the battery is grounded to the frame already, but this is typically through a #10 or so wire that will melt if you try to jump the backhoe with it.) Use more corrugated tubing over this cable.
In the back, attach the Anderson terminal to the long piece of welding cable. Put the corrugated tubing over the cable. Plug the terminal into the connector, and then route the tubing+cable to the front of the truck. Avoid moving parts and anything that gets hot. Get the thing secured to the frame or body at least every 12 inches. At the front, crimp a lug on the cable and attach it to the positive terminal of the battery.
You may want to make a cover for the Anderson connector on the bumper so it doesn't get mud and water in it. You might be able to find a vinyl tube cap that will stretch over the end. Or, instead of bolting the connector to the bumper, get a small plastic toolbox and bolt that to the truck. Cut a slot in the side of the toolbox for the cables. When you're not using it, put the connector in the toolbox and latch the lid.
To use the rig, make sure the jumper clamps aren't touching and then plug in the Anderson connector on the jumper cables to the one on the truck bumper. Connect the positive clamp to the backhoe battery and the negative one to the backhoe frame, and start it. To disconnect, unhook the negative clamp first, then the positive, then the Anderson connector.
You can probably get all of this except the Anderson connector at your local electrical supply house. You can get the Anderson connector and terminals here: http://www.delcity.net/delcity/servlet/catalog?parentid 2&page=1 You probably want the 175 amp kind. If you do decide to go with thicker wire, you can go with the 350 amp ones.
Good luck!
Matt Roberds
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<<I would like to run two permanent cables to the back bumper of the truck I would like to run two permanent cables to the back bumper of the truck.>>
Be extremely careful to protect the cables mechanically throughout their length, and to protect the terminals against accidental contact. If a piece of metal accidentally shorts out cables that big, powered from a big battery, the cables can melt and throw molten metal, and the battery can explode, spraying sulfuric acid in all directions.
Starting-fluid may help. It is available from truck supply stores, in pressurized spray-cans. Be careful with it, as it is highly flammable, and the pressure is high inside the cans.
Dick Alvarez alvarez at alumni dot caltech dot edu
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Im from the UK so dont know what a backhoe is. I would suggest checking the charging system , is battery AMP/HOUR capacity low ,or quite simply charge the battery from the vehicle system as done in caravan trailers. cheers,Indian.

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robert grant wrote:

AFAIK, we (Brits) call backhoes by the manufacturer's name - hence, JCBs (like hoovers being, well, Hoovers)...
Back to the OP, I may be being a bit wimpish but I would certainly protect the welding cable running down the truck frame with a fusible link or fuse. The type fitted to electric fork lift trucks are ideal. Do a Google on fork lift fuse, if you aren't familiar with them.
Incidently, I also fit fuses like those to the battery bank for household inverters - having seen the after effect when a floor-full of deep discharge batteries tries to dump their stored energy into a faulty inverter. Luckily no one was in the room at the time - they just heard the bang..
Another thing I would fit for safety, if this could be used for other things besides the backhoe, is a suitably rated rectifier in the line - trying to jump start a 24v truck can otherwise be exciting.
Although I really ought to be good and use the right non-reversable plug and socket, if it were me, I would probably just fit a pair of insulated screw-down terminal posts at the back of the truck.. As I would soon lose the special cable, (or someone would half-inch it..) and it would be easier to get hold of a replacement set of normal jump leads. They can also be used to jump start the truck, from a passing vehicle, after forgetting to switch off the battery heater..
--

Sue













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robert grant wrote:

<snip>
http://science.howstuffworks.com/backhoe-loader-image1.htm
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Chief McGee wrote:

Would it be cheaper or more practical to mount an extra set of batteries on your trailer? You could use a lighter set of cables from the truck to charge them while traveling. A 110 volt charger could charge them overnight if you a convenient outlet. Then you could use a regular set of jumpers to start the tractor. We have to jump start motors frequently in the summer. We use 2/0 welding cable. I think my cables are 16 footers.
Dean
-
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Dean Hoffman wrote:

I was stationed at Ft. Greely AK. in the early '70s. There were 20 amp AC outlets by any place on base you were allowed to park overnight. You were allocated a 20 Amp, 120 volt circuit to power a battery blanket, dipstick heater, and lower heater hose heater. This was the US Army cold weather test site and the concept worked fairly well. In the winter time you had to keep the engine tuned up, and it helped to put heavier battery cables in the vehicle. Most of the guys used 2 AWG welding cable because anything heavier was too stiff to bend in the cold weather.
--
Former professional electron wrangler.

Michael A. Terrell
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This is the best solution. I did the same thing. Truck, with 7 pin trailer plug, already has a full time hot feed. Just get a batterybox and deep cycle battery. Mount on trailer tongue and hook up to hot feed. You will always have a charged battery on the trailer. That with a can of starting fluid and I could always start my massy ferg 50C. even at 10 degrees.

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Instead of running a circuit for jumping the backhoe. Consider just running a couple of small wires to keep the batteries warm. I would think you would need nothing more than 10 guage to do this. A few minutes of chagre time before cranking should be all it needs to get the batteries up to temp. If this will not take care of your needs it means the backhoe batteries and/or charging system is kaput..
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O yeah if you decide to do this remember to disconnect it before starting the backhoe or you will burn up the wires. 10 GUAGE WIRES MAKES LOUSY JUMPER CABLES.. Actually I think your problem is a bad battery or charging system on the backhoe.
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The first thing to note is that this is *not* caused by a cold battery. If the battery is a problem, it's not just because it got cold.

Bad idea, and *all* discussion of how to do should be ignored, because 1) they all fix the wrong problem, and 2) every single solution is risky in ways that are not worth risking.
Running small cables that length is a waste for as a "boost" for starting. Any such cable should be used to charge the battery, and should be /disconnected/ before you engage the starter on the backhoe. Any such cable that is permanently mounted should be *very* well protected, both electrically and mechanically.
But all that does is put a bandaid over a few symptoms instead of correcting the problem.
There are two possibilities for the root cause of hard starts. One is that the battery or the charging system is faulty. Cold, as such, isn't the problem if you aren't seeing temperatures of -45 to -50F. Lots of people who live in Fairbanks AK, or other interior Alaska locations, don't bother with battery heaters and have no problem with a cold battery (even at temperatures as low as -70F). I don't think you are out running a backhoe at -50F...
All that happens when its that cold is the battery has *much* less charge available, and if the engine isn't warmed up and ready to start, the battery gives up the ghost before the engine runs. That is actually a _good_ thing, because if the engine isn't warm enough to start you *don't* want to warm it up by running it!
Hence, check out the battery and charging system first.
Second, if you are talking "cold" in terms of anything above 0F, get the engine tuned up. An engine should be able to start *well* below any temperature that you actually want to start it at!
At sub-zero temperatures you need to think about pre-heating the engine before starting it. And despite what I said above, you might as well pre-heat the battery too. That is particularly true if the backhoe often sits unused for any length of time. In that case it might well be hard to start even when warm, and takes a little more battery charge to do it.
As to how to pre-heat the engine... you'll have to be inventive and consider your specific situation. Typically airplanes, as one example, are pre-heated with a diesel fired Herman-Nelson heater. Typically cars and trucks are pre-heated with electrical heaters. You can install a heat pad under the battery (or better yet install a trickle charger), *and* install one of a number of different electric heaters available for the engine. Circulating heaters should be avoided. Block heaters that screw into a plugged hole in the block are the best. Ideally that would all be plugged a handy power outlet for least an hour before the vehicle is started.
However, you could power it with a portable generator too, if the trailer is not normally parked where electric power is convenient. Except that you then have to physically be there to heat it up, while a timer can be used with a regular power outlet to allow instigating a future heatup at any convenient time.
Another point that I would suggest is *always* starting the backhoe *before* you travel with it. That means any problem will be discovered before you are on the work site. It also probably means your truck is not yet hooked to the trailer? If so you don't need long jumper cables at all, because you just nudge the front end up close and jump start it *before* attaching to the trailer.
--
Floyd L. Davidson <http://web.newsguy.com/floyd_davidson
Ukpeagvik (Barrow, Alaska) snipped-for-privacy@barrow.com
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Sidebar: since anti-freeze is only rated to -40 degree F, then what is used in Alaska for -50F and -70F?
"Floyd L. Davidson" wrote:

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Proplyene glycol based antifreeze is good down to -60F, while ethylene glycol is good down to -84F.
That's the "freeze point" when mixed 60:40 with water.
--
Floyd L. Davidson <http://web.newsguy.com/floyd_davidson
Ukpeagvik (Barrow, Alaska) snipped-for-privacy@barrow.com
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