Wiring for dump trailer

buzzyngFebruary 27, 2014

I know this is related to house wiring so if there is another forum elsewhere on internet then feel free to redirect me.

Right now, while I have some good weather, I'm taking a break on the building part and moving dirt around to level out around the foundation.

I have a 5yd dump trailer and can get 2 dumps out of one battery (it's getting old) and 5 dumps out of a new one I bought. After the 7 dumps, I'm done for awhile to plug them into chargers.

I would like to use my portable generator to keep going and wanted to know if someone could show/tell me what is needed to wire from gen to the pump. There is a trickle charger built into the compartment that I can plug into but if the battery is dead, it still wont operate. I can post a pic of the current config if that would help.


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I don't have a feel for how the system works. Is there anything that tells you the HP or current draw of the pump motor? Does your genset have a battery charger provision?

Are you towing the dump trailer with a truck or a tractor? If so, maybe you can run the dump pump from the vehicle battery/charging system?

    Bookmark   February 27, 2014 at 3:36PM
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the dump trailer is towed my a truck and it does tie into charging system but is just a trickle as well and wont keep it charged during operations. I have a fast charger that I can plug into gen but I still have to wait for it charge the battery though.

Ideal situation is that after both batteries are drained, I plug them into charger while using the gen to continue running the pump.

I'll get the specs and pics to post


    Bookmark   February 27, 2014 at 4:31PM
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No bright suggestions at the moment. Lead-acid storage batteries should be fully charged at all times for maximum life. Partially charged or discharged batteries will experience sulphated plates.
Keep fully charged as much as possible.

Here is a link that might be useful: Battery

    Bookmark   February 27, 2014 at 7:53PM
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First off, there is no battery charger built in to the genset? Some have them.

Honestly, I'd be thinking of hooking some fused leads to your truck battery and just using that as a power source. Just forget about the other batteries for now. Is there any reason that you can not do that? It is going to be faster, easier and less expensive than anything else that I can think of.

All you need is some wire, a fuse holder, a fuse and some connectors to break out the dump battery and hook up the truck to it. Post the motor current draw and someone can tell you what wire you need. In fact, you can run one fused wire to the truck battery and the other (Unfused) to somewhere to the rear of the truck frame so you need less wire. On the other hand, just hooking both up at the battery takes advantage of some disconnect hardware tailored to that use. You might also find an empty fuse slot in your main fuse box that you can use.

What kind of batteries are you using on the dump trailer, deep discharge, flooded-cell? Deep discharge batteries are not built to charge quickly. You might be best off charging one while you are using the other.

Fast charging batteries is often not good for them, but I don't know if you are really "fast charging" with your fast charger. For a flooded cell, lead acid battery C/10 is a general rule. C = capacity in amp-hours and the output number is amps. A 20 amp-hour batt should thus be charged at 2A or lower for best battery life. Yes, you can muck with the initial rate (C/5) and go faster, but you have to slow down as the battery charge improves.

I don't know if you can run the pump directly with a battery charger circuit. It really depends on how the battery charger is designed and how much current you need. An old-fashioned, dumb constant-voltage charger might work if sized properly. If not sized properly, smoke might come from somewhere. If you are really lucky, a few exciting flames too. Then the charger won't work any more, only one thrill per charger in that mode. A fancy-pants, modern, microprocessor-controlled charger might decide that your battery is defective, since it looks like a motor, and disconnect itself.

You could build your own charger in a couple of ways. (1) You can get 14 V surplus transformer and surplus rectifiers or a bridge rectifier and build a simple power supply to plug into your genset. It would set you back 20-50 bucks for the parts. (2) You can hook an automotive alternator to a gasoline motor that you have lying around after you have built a frame for the whole contraption. It has been done many times. An alternator with a built-in voltage regulator would be convenient, but you can use one with an external voltage regulator off the same car. It should probably be an old car because at least some modern ones have voltage regulated from the main engine controller.

See, running wires from your truck battery is looking easier by the moment :-)

    Bookmark   February 27, 2014 at 8:00PM
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Does the truck you use have a standard 7 wire trailer plug that is wired correctly? A correctly wired 7 wire plug will have one terminal that is designed to provide accessory power, and its typically used for interior camper lights or other accessories. This is not the wire that is used for the running lights or signals.

If you take a look at this wiring diagram, the one you could use for a charge wire would be the one labeled "auxiliary power".

Most factory wiring setups use a 10 gauge wire for the accessory power feed, and it may have up to a 30 amp fuse on the circuit. If you use a standard trailer connector to wire this up to the trailer, you should have plenty of amperage to keep the dump trailer battery charged.

If you don't have the wiring on your truck, any competent RV dealer should be able to install a properly wired 7 wire trailer connector.


    Bookmark   March 1, 2014 at 8:24AM
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I am assuming that the truck might not be running long enough to keep the battery charged. The truck will be running when he is getting ready to unload so the alternator could be used to provide plenty of power. I really have no idea if 30 A will power the trailer pump directly.

OP, are you just loading the trailer with a bobcat and moving the fill a short distance. Are you just moving across a lot?

    Bookmark   March 1, 2014 at 8:56AM
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THanks for all the feedback and need to ask some more clarification.

I'm loading with a skid loader or excavator (dirt and rocks) and moving around 5 ac lot.

If I run to my truck battery, will the alternator be able to keep up the charge since dumps are relatively close together time wise ... or do I just keep the truck is running the whole time?

Today I got 7 dumps out the 2 batteries in about 75 min and then I moved onto something else. I'm attaching 2 pics that shows the compartment and pump sticker

I do have a 7 pin wiring harness.

thanks for the help

    Bookmark   March 3, 2014 at 12:58AM
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Close up of the pump

    Bookmark   March 3, 2014 at 12:59AM
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Is that 28.0 amps? How long does it run to run a dump cycle?

Full-size PU alternator outputs vary a lot from 100 amps to well over 200. I assume that is true for larger trucks as well. In addition to that, some are designed to be better at lower RPM than others.

I'd think that the truck alternator can keep up with a 28.0 amp pump and keep the battery charged if you keep the truck running while running the pump. Shut it off while you are loading. Since there are unknown variables, I advise checking your battery, during the day and at the end of the day, with a hydrometer if the battery is not sealed. Maybe think about how to best check the voltage if it is sealed. Does the truck get some highway time to and from the work site?

    Bookmark   March 3, 2014 at 10:57AM
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If you charge it using the truck and the alternator can't quite keep up you will still be ahead. You might still get twice as many dumps before it quits.

Nearly all modern trucks have at least a 100 amp alternator, and many have one with much higher output. However, you will be limited by the fuse on the auxiliary circuit if you use the 7 pin plug.

The 10 gauge aux trailer wire itself should be good for up to about 60 amps at 12 volts, but I have never seen them fuse it more than about 30 amps. However, if you already have the 7 wire hookup it will be easy to try it out and see if it charges enough.


    Bookmark   March 3, 2014 at 3:29PM
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@ionized 28.0

amps is correct

Haven't time a dump cycle but my guess is probably around 45-60sec or so to reach full height and then slightly faster coming down

pretty sure my truck (2500HD) has a 105A alt

it only takes about 15min to get to site so not alot of highway time


my plug, a 7 pin (blade style). The plug on the trailer doesn't run into the battery compartment, just the lights/brakes. So I would need to rewire a new plug to use the aux power or still run something to the truck battery?


    Bookmark   March 3, 2014 at 10:45PM
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If this were my temporary problem, I'd just make a jumper cable with some of the least expensive cable that I could find of sufficient gauge and some clamps. The latter can be found in many places. If you will continue to use it in the future on a reagular basis, it merits more investment. Note that it is probably a better way to run things in the long run because you don't have to purchase and maintain a separate battery.

    Bookmark   March 4, 2014 at 10:54AM
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Thanks. This is a long term solution need because I use the dump trailer for side work as well so having it setup properly would be best. Can you provide the details of how that would be? tx

    Bookmark   March 4, 2014 at 12:22PM
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I don't really know anything about trailer wiring so I don't know if a standard trailer plug can be used to provide 28+ AMPs.

Hooking into a vehicle electrical system is going to be very vehicle-specific. The most important thing to remember is that you want a fuse or circuit breaker as close to the the connection to your vehicle's system as possible. If you don't have that, your risk of a vehicle fire is higher. Otherwise, it depends on what it looks like under the hood. Others here or on a truck board (assuming this is a PU) might be of more help. A PU truck board for enthusiasts for your particular truck will be most useful. There may be an empty slot in the main fuse box or relay center that you can use to make a really neat installation. otherwise, you could change the positive battery terminal clamp or harness to one with an additional connection and install your own fuse or circuit breaker.

From either of those sources, you'll have to find a protected place to run the wire to the back end of the truck. The negative connection can be made to the frame. With any kind of luck, you can find a hole to insert a small bolt with a nut on the other side to hook a ring terminal to. Actually, I'd probably install a stud. You can find lots of pictures on the web that show ground strap installation. Most of them have to do with connections to the battery or alternator, but it is the same problem, really. You'll need to clear off some paint, make the connection, and then it might be a good idea to repaint over the frame and bolt so you don't get corrosion. This is especially true if you live in an area where they make copious use of halide salts to keep the roads clear of ice.

After that, there is the connection to the trailer. You need some sort of connector that won't accidentally short on the truck body or frame. Ideally, you can mount one end to the truck body or frame where it is accessible. The other connector can hang with the rest of the trailer wiring. The type of connector that I have in mind is often used to connect fork lift batteries and the like. The security vehicles where I work have them hanging out the front end of the vehicles so they can easily hook up jumper cables to jump start employee vehicles. See Anderson #6331G1. Again, others might have better ideas.

Lastly, you run wires to the pump over the trailer frame somehow.

    Bookmark   March 4, 2014 at 8:13PM
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ionized provided good input, but it is a much simpler process if you already have a 2500 HD with trailer wiring. I assume you don't need a trailer brake controller, because that would be an additional item.

GM usually wires the 7 pin plug all the way to the back of the truck on the pickup and mounts the plug on the bumper. You may have to buy a kit with the fuses and relays to activate the aux and brake controller wires, but there is no need to run any wire for anything on the truck. If the fuses and relays are not already there you just plug them in and the wiring is now active.

As I already mentioned, one wire in the trailer plug is an auxiliary wire for charging a battery or running lights on the trailer. It is probably fused for 30 amps, but you would have to check the GM manual.

Then you need to buy a 7 wire trailer (male) plug at Wal-Mart, Advance Auto, or any other parts store. You will only need wire five terminals to the truck -
Wires you need to connect from the plug to the trailer - left turn, right turn, running lights/brakes, ground, auxiliary power
Terminals you can leave open - trailer brakes, backup lights (unless you have them on the trailer)
The aux power and ground should use a 10 gauge wire and the others can use 18 gauge wire.

If you are not comfortable wiring up the trailer to the plug, take it to any RV dealer and they should be able to do it very quickly.


    Bookmark   March 6, 2014 at 5:57AM
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Do you suppose there is some connection between the fact that the typical trailer circuits contain one that will support 30A and the dump pump uses 28 rather than, say, 35A?

    Bookmark   March 6, 2014 at 2:52PM
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