Power supply to rear of Truck

[Mfitz]

I have a 2015 Ford F150 with a 7 pin trailer plug and a travel trailer with 2 6v Trojan batteries for boondocking. Ford doesn't wire the 7 pin to do more than just keep a trickle charge, and I want to send more power to the trailer to give the batteries a heavier charge when driving- I want the batteries fully charged when I park it. I'll be installing a 100watt solar system as well to help keep the batteries functioning for several days at a time.

I also want to set up a Viair compressor drawing 30 amps max in the bed of the truck so I can reach both the truck and trailer wheels. Here is my plan and my questions:

I will run a 4ga power feed from the truck battery to a solenoid (for switching with ignition), then to a Bussman manually resettable breaker under the hood, then back to the rear of the vehicle. I would use a winch-type plug to connect it to a similar plug on the compressor when needed, and a similar plug I'll wire into the trailer lead when towing. I'll probably disconnect the hot lead on the 7pin just to make sure there aren't any issues.

Questions:

How does this sound for a plan? I'm trying to keep it simple.

What size breaker should I put under the hood? The compressor would want a 40 amp but I'm not sure what to do for the batteries, and it will all run off the same breaker (but never at the same time).

I assumed I should I run a negative wire off the battery to the plug at the rear of the truck for the compressor, but I won't need one in the trailer lead to the batteries. Is this correct? If so, does the negative also have to be 4ga or could I use some 8ga I have extra?

Thanks for any suggestions, remember I am pretty new to this and want to keep it simple.

 

[Bbasso]

There's plenty of info that also has been beaten to the point of death on this forum alone.
Please take the time to do some research, at this point of time most of the replies would be cut and paste...

 

[SnoViking]

Check out "dingy" chargers. They're what RV use to charge the batteries of the cars theyre pulling in-tow. They're usually cheap and you can get different amp models.

 

[Mfitz]

Thanks all for the advice. I did do some searching before posting but didn't find anything on my specific situation, and I just got lost in the weeds of more technical electrical posts.........

I should have said I hope to get as much charge as possible while towing, rather than getting full charge.

If anybody else thinks of something I should consider before doing this, let me know.

 

[dwh]

The fuse/breaker is to protect the wire. Since both the positive and the negative will carry the same amps (it's a loop) you can't have one be half the size of the other. Well...you could. You could use #8 and #4, but you would have to fuse the circuit to protect #8 - so the #4 would just be wasted overkill.

Also, if you run a fat positive to the trailer batteries, you're gonna need an equally fat negative to go with it.

And, you'll need a breaker at each end. The breaker under the hood isn't going to help by itself. Even if it trips, that won't stop the excitement if a short is still being fed power by the trailer batteries.

 

[Mfitz]

The fuse/breaker is to protect the wire. Since both the positive and the negative will carry the same amps (it's a loop) you can't have one be half the size of the other. Well...you could. You could use #8 and #4, but you would have to fuse the circuit to protect #8 - so the #4 would just be wasted overkill.

Also, if you run a fat positive to the trailer batteries, you're gonna need an equally fat negative to go with it.

And, you'll need a breaker at each end. The breaker under the hood isn't going to help by itself. Even if it trips, that won't stop the excitement if a short is still being fed power by the trailer batteries.

Equal sized feeds for the main line makes sense now, thanks. I also hadn't thought about having a breaker at both ends, but this makes sense as well. It would need to stop electricity from both ends should there be a short in the middle. Thanks!

 

[IRISH]

you tube sales general ( this is the Australian direct you tube channel ). look for The Ultimate Dual Battery System Education Video! It has a lot of good options and ideas.

 

[Ducky's Dad]

You might look at the Ctek D250S Dual. It will charge the trailer batteries first at a maximum of 20 amps to the trailer, so that you can wire the trailer for that max current. Once they are fully charged, the full charge current goes to the starting battery. The D250S is also an MPPT solar controller, and can charge the trailer and starting batteries. Call Ctek tech support for details and wiring diagrams, because they have a bunch of stuff that is not on their website. They also have a new D250SA, designed to optimize AGM charging, but it is not sold yet in the U.S. Available now in UK and Australia.