Electrical truck to trailer connection question

[NanciL]

Can I use an extension cord to connect between my truck connector and my trailer cable connector ?
If yes do I have to worry about a voltage drop if the distance is too long.
I park my trailer in a trailer barn that I built several years ago, and this year I added next to it an attached truck port where I now park my truck.
Each time we want to work in the trailer or have heat/lights on in it, I have to back the truck out and back it up to the trailer to plug it in.
I am thinking that if I had an extension cord, I could leave the truck parked in the truck port and then just using it , plug into the trailers cord.
I have space to run under the side of the two buildings, but haven't measured the distance I would need for the extension.
If I can do this; what is the maximum length I can use for the extension cord, (naturally I will use the shortest that I can)

Jack L

[allen8106]

Jack,

While definitely no expert in my humble opinion as long as you have the 7 pin connectors you should just be able to what you are thinking of. The #4 pin is for 12 volt charging. As long as you have a wire hooked to both #4 pins you can plug the connectors in as you suggest. My only recommendation would be to up size the wire by two wire sizes.

[NanciL]

Lantley wrote:
Now that you have built the barn follow through and install electricity in the barn. 20 amp circuit would do 30/50 amp would be better.
Leave battery in RV and keep trailer plugged in 24/7.
Installing electric would be the professional thing to do and eliminate monkeying around with connecting RV to truck etc.
With electric installed you could go in and out of the trailer as you please without having to do anything.

That sure would be nice and I would do it in a heart beat, but there is no power any where near it.
It would solve all my problems and I wouldn't have people second guessing me too !

Jack L

[jrnymn7]

http://www.calculator.net/voltage-drop-calculator.html?material=copper&wiresize=2.061&voltage=12&pha...

[YamaDooed]

If your just hooking up a just a two wire charge cable.Go buy a 30' 12g extension cord cut the ends off and wire to your male and female seven pin.

[2112]

To answer your question, yes you can do what you are asking.
You can purchase the two mating connectors, the proper length of cable and fabricate your umbilical. What is the largest gauge wire the connectors will accept? My guess is you may be able to squeeze an 8 AWG in it but I do not know.
Doing in this way you will have the voltage drop across the wire from the battery, relay, wire to the connector, connector itself, the wire you added and another connector.

I have a question. Do you own a set of jumper cables? Too short?
Determine how short and go to the auto part store and get a second set at least that length. Find two short pieces of 1/2" or so copper pipe. connect one set to the TT battery terminals, you don't need the battery. Connect the other set directly to the truck battery. Connect the two jumper cable ends together by clamping them to the copper pipes.

This will provide the least voltage drop and cost you less with less work.
Just my humble suggestion.

[Lantley]

Now that you have built the barn follow through and install electricity in the barn. 20 amp circuit would do 30/50 amp would be better.
Leave battery in RV and keep trailer plugged in 24/7.
Installing electric would be the professional thing to do and eliminate monkeying around with connecting RV to truck etc.
With electric installed you could go in and out of the trailer as you please without having to do anything.

[ol_Bombero-JC]

Guy Roan wrote:
I can't help the OP but I don't understand why people feel they have to chime in when they evidently don't know the answer.
He/she asked two simple questions and the first four replies didn't give him the answers he was looking for but felt they had to chime in.

Guy

Now - both you and I have also chimed in....without the answer!..:S

~

[CA_Traveler]

The trucks alternator and charging voltage will be mostly determined by the trucks battery. If it drops to say 13.6V then there is less voltage difference to charge the trailer battery. The low voltage involved means that you need bigger wire.

Sure you can calculate the voltage drop of the wire but there are other factors including the batteries and truck wiring. Can you connect directly form the truck battery to the trailer battery? ie The shortest possible distance.

I would beg, borrow or steal (not really) a cord or other wiring and try it. Even if the trailer charging is limited you might get enough amps to allow usage of the trailer while maintaining the battery.

[Guy_Roan]

I can't help the OP but I don't understand why people feel they have to chime in when they evidently don't know the answer.
He/she asked two simple questions and the first four replies didn't give him the answers he was looking for but felt they had to chime in.

Guy

[NanciL]

CA Traveler wrote:

NanciL wrote:
Can I use an extension cord to connect between my truck connector and my trailer cable connector ?
Yes
If yes do I have to worry about a voltage drop if the distance is too long. Yes Use a 10ga cord, 25' should be long enough but measure first. There will be some additional voltage drop.

Even if you don't want to hear this: I would never work inside an enclosed area with a engine running due to carbon monoxide among other things. If power is not available my choice would be a portable 120V gen outside.

Many thanks CA Travler

I appreciate your answers to my questions.

I agree with you 100 percent on not working in an enclosure with the truck running, but in this case the trailer is in one building and the truck is in the next one, and there is wide open spaces on both of them. Visualize two car ports side by side

Jack L

[CJW8]

Simple answer is yes. buy the proper length 2 conductor cord, Attach appropriate trailer plugs on both ends and go to work.

[beemerphile1]

It is unclear to me exactly what you want to do. Maybe jumper cables from the truck would be simplest solution. Personally, I would either plug it in or install battery.

[BFL13]

Turning the truck around saves you wire for the length of the truck. Pretend that is 22 ft. So yes, just add 25ft of #6 wires (or whatever gauge) to be the extension cord, using only pin #4 and ground in a set of 7-pin connectors. Now all same except you don't have to turn the truck around.

The extra voltage drop will depend on the current drawn at the time for whatever you are doing. Use fatter wire for the 25 ft extension if it drops too far from what it is now (ASSuming that it is ok as is with truck turned)

The biggie is the heat mentioned. The furnace might be 7 amps right there increasing voltage drop from just lights. If it is just lights no problem, but what work is being done? Tools usually need 120v. If you have 120v then just run the converter to make the 12v.

The scenario is unclear. 🙂

BTW, I have run the truck for over an hour at idle with a 1000w inverter attached powering a 35 amp charger that needs 600w so I know that is an option. Long 120v extension cords are not nearly the problem that long 12v cords are for voltage drop.

[wolfe10]

Jack,

The reasons for answers all over the place is there is NOT an industry standard for truck/trailer wiring. Many only come with running, brake and turn.

If you have a "battery to battery" positive and ground wired into the pig tail, sure you could make up a longer pigtail-- perhaps with just the positive and ground (since you do not need running, brake and turn lights).

But, the next question is do you have 120 VAC in your storage area-- where a converter/battery charger could do this.

And if you do a large gauge truck battery to trailer battery or 12 VDC distribution panel, be sure you have an in line fuse at both ends-- right at the battery, as either battery should be hot (assuming the trailer battery is installed).

The more details you give us on how yours is wired, the better we can answer.