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For some reason the the trailer batteries are not getting charged. The 7-way plug on the truck shows the proper voltage as tested with a lighted probe by U-Haul (I took the truck there to check). The supposed current wiring is setup to charge the trailer batteries (3 batteries) when the running lights are on on the truck.

The trailer has Equalizer powered leg retraction/deployment system with an up/down switch. I used a spare battery to make sure the switch was not the problem.

When I connect the trailer plug into the truck's 7-way receptacle (there are two and neither is sending 12v to the batteries), I can't get the switch to work. The truck's two batteries should be able to activate the switch. This leads me to believe that the trailer plug is not wired right. Not having a schematic etc. I don't want to guess which is which.

I have decided to direct wire from the truck's battery to the rear bumper area and then have a separate wire from the batteries on the trailer to plug into the one from the truck.

The truck is over 20'. Questions:

1) Will an 8 gauge wire be enough from truck to rear bumper area?

2) Will 10 gauge wire be ok from trailer to rear bumper area or should I use 8 gauge?

3) What size fuse should I use?

4) You see any potential problems with this?


I just had a thought. If the batteries are supposed to get a charge from the truck when the running lights are on, wouldn't the running light wire and the battery charging wire be on a common terminal in the trailer plug? If so, I did not see that when I took the plug apart. Unless they used a separate terminal on the receptacle with a wire to the battery and a separate one in the trailer plug for the batteries. Somehow if the latter is true, then the connection is not being made.



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Using the running light circuit to charge the batteries on the trailer seems a might skimpy to me.

Make sure the trailer batteries are in good condition and fully charged, as that little 16 or 18 ga. running light circuit. is not going to provide much current to charge 'em.

You said you tried a third battery and that worked. Try taking one of the other two and run your test again.

Otherwise, 10 ga. should be ok, you'll have problems trying to get 8 ga. on the connectors inside the plug and receptacle. Use a 30Amp self-re-setting circuit breaker (common auto parts store item) as near the source (truck battery + or alternator +) as possible.

what about the tow vehicle? is it pre-wired to supply a direct connection from the battery + or alternator + to the receptacle?

Do all other functions work ok? what happens to engine speed when you plug the trailer connector into the truck? If the trailer batteries are low, the alternator output will get dragged down, and the engine should speed up to compensate (like when you connect a dead car for a jump). Do the running lights seem dim? Unhook the batteries and check again. Oh, and how are the batteries grounded? to the trailer frame? If so, have you got a good ground from the trailer frame back to the truck?


Jason.
 

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Raffy:

I don't know much about the type of setup you are speaking of, but one thing jumps out at me. What size are the contacts in the plugs? What size wire is leading to them? Wondering if there is some type of voltage regulation to the charge circuit to limit the charge current to the trailer batteries. If you had run down batteries, and hooked them to full voltage from the truck's alternator you could have a pretty high current, and would need heavy wire. Seems to me that unless there is very heavy wire to the connectors, it would be overheated unless there is some type of current limiter involved.

If you are running seperate charge wire direct from the truck battery, use this table:
http://www.rbeelectronics.com/wtable.htm

That shows that 10 ga. wire would be good for 50 amps at 20 ft. If you think the amperage would go above 50 amps, or the length of wire would be over 20 ft, then I would use 8 ga.
 

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Discussion Starter #4
wiring non-LT

The 3 trailer batteries are connected to each other. I believe they are all discharged. I used a spare (4th) battery that I had and connected via jumpers to one of the trailer batteries and the switch worked. The batteries are deep cell so it would normally take longer to charge. Unfortunately, the trailer sits in a storage yard so no power access to charge them.

I'll check into the other stuff you mentioned.

Thanks,



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Discussion Starter #6
wiring non-LT update

Well a little more work on my part and I believe I figured it all out.

Yesterday when I took the trailer connector apart, I found 3 loose wires not tightened to terminals (with screws). So I guesstimated and tightened them down one on each terminal. then checked the lights and found the right trailer lights were not working. So I swapped two wire positions and everything worked except charging the batteries.

Today I went back and hooked up the trailer again and turned the running lights on. Still no charge. Opened the hood and checked the fuses. Sure enough fuse #19 was blown (I had checked the fuses yesterday before the wiring guesswork). This fuse is labeled trailer battery. They had a 20 amp fuse in. I only had a 25 amp mini fuse and used that. Sure enough the switch on the Equalizer worked so there is power to the batteries on the trailer.

Should I replace the fuse and go back to 20 amps?



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RaffyK said:
Should I replace the fuse and go back to 20 amps?
It's always best to start low. I would replace with another 20 amp fuse, and see what happens. If it doesn't blow right away, chances are that's the correct rating. If it blows right away...either it's too small, or you have a short.
 

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Once you're sorted out look into a small solar cell for the top of the trailer, it'll keep you topped up in storage. They are being used a lot by the trailer boat set with much success. Try West Marine.
 

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Help with wiring......

Raffy, on my truck there is a fuse that runs from alternator
which runs in the wiring to the trailer plug....Check the fuse, I know if i pull the fuse or its bad it wont charge the trailer batteries....
Just a thought
 

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sounds like you figured it out i appoligize for the delayed previous post...
 

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Discussion Starter #11

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Keith said:
Once you're sorted out look into a small solar cell for the top of the trailer, it'll keep you topped up in storage. They are being used a lot by the trailer boat set with much success. Try West Marine.
Raffy,

Keith makes a great point about hooking in some solar panels. I have them for charging the batteries that open and close the gates on our property. Each gates runs off an interstate marine-grade battery and the panels keep the battery charged. I can get manufacturer details for you - as proud as they are of electric gates not sure which costs more marine or gate supplies :eek: :eek:!
 

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Discussion Starter #13

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