# Wiring up Dump trailer for Battery charging



## carsrus

First thread here, great site.

We have a Dodge PK with factory hitch wiring. What do I need to have the vehicle charge the Dump trailer's battery? Just run the 12v wire from the truck to trailer battery? Customer was told he needed some kind of box to make it work and pretty expensive. I know that on Campers we just run the 12v wire to Battery but not sure if the Campers are already set up with whatever box is needed, TIA.


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## EIB

What does the factory wiring have? Is it a 4 way, 6 way or 7 way? If it is the 7 way, it will have a 12 volt hot to charge the battery. If it doesn't, put a 7 way on it and run a fused hot feed from the battery to the connector. It would also be a good idea to put a switch on the wire to turn it off when it's not in use. The pin on that connector will corrode faster if its not done.


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## carsrus

The factory wiring is the 7 pin and it already has the 12 volt hot wire running through a relay and 40 amp fuse I believe.
I just have to run the 12 volt wire on the trailer side to charge the battery, and it should work. I just wonder what type of box they're recommending! Could it be an isolator so when the dump on the trailer is working not to discharge the truck's battery?

Thanks.


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## EIB

I think it is just a junction box for the wiring. I will look at my equipment trailer and let you know. The dump trailer should have already been wired for it.


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## Alan

I just did a trailer like that. Run a substantial, like #10, wire from the 12v hot lead in the trailer connector right to the battery positive. If the hto wire on the truck side is always hot when the truck is running it is a good idea to shut hte truck off when dumping. With a heavy load the trailer pump can draw current enough to put a load on that charge wire. I know that it will trip a 30 amp breaker, so I suspect it would take out whatever fuse you had in there. Mine is switched through a heavy solenoid and I shut the charge leg off now that I know how much it can draw.


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## carsrus

I don't have the truck/trailer now, it's one of our customers. When I get him back I'll check it out a little better. I've been checking into isolators (which I was not familiar with) and that might be the ticket. I believe the isolator is used to charge the Dump trailer's battery when vehicle is running, and yet prevent the vehicle's battery to be discharged when the dump is used by not allowing the pump to draw current from the vehicle's battery.

There are other ideas like running heavy gauge wiring and disconnecting the trailer connector or shutting off the truck. Also like the idea of running it through a solenoid.


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