sunnysday

Can someone please tell me how to get my F150 2016 (which has a tow package) to charge my RV battery?
My dealership service is not helpful, everything works but the batt charge.
Thank you,
S

old_programmer

I assume the connector has 12v on the Aux line (pin 4). According to what I was told by Ford this line is only meant to maintain the battery and run a few low current things like clocks. The wire that is used for the Aux line appears to be 18 or maybe 16 gauge based on the outside diameter of the insulation. At that wire gauge it would take a long, long time to charge a partially depleted battery. I needed more current to run my fridge while driving so I disconnected the Aux line in my trailer's junction box and ran my own. I ran a 10 gauge wire, circuit breaker and relay from the truck battery to the trailer. In hindsight I wish I had used 8 gauge for more capacity but what I have works well enough for my current trailer and needs. The subject came up when I was at my dealer for something else and they said they had to do something similar for another customer who owned a fifth wheel.

Apples

Random thoughts from an amateur directed at the OP...so take it with a grain of salt.

It is almost worthless to attempt to charge an RV battery from the tow vehicle unless the RV battery is an old-school flooded-cell lead/acid type that you can add distilled water to. Even then, it may add undue electrical stresses (for lack of a better way of putting that) to the vehicle's charging system. You might be sending some current downstream and prevent the RV batt from being fully discharged, but it will never fully charge in this setup. Chronic under-charging a battery can kill it. Batteries like to be kept full, and not 95% full, but 100-101% full, then floated, depending on the battery type at either 13.4 or 13.6/7V.

Otherwise, to fully charge any modern battery type such as an AGM requires a charger type (110V or solar charge controller) using a microprocessor utilizing a 3-step charge profile.

It is a small investment, yes, but one 100-watt solar panel and a good quality solar charge controller and PROPER-sized copper stranded conductors on and in your RV will see that battery fully-charged and well-maintained.

/random thoughts

Shaggy1970

On my 13 there were two fuses located in the glove box when the truck was new that had to be installed in the fuses box in order to allow the truck to charge the batteries while under tow.

old_programmer

That's not the case from 2015 up. The charge line is driven off and controlled by the PCM that also handles the smart trailer detection. No fuse based on the schematics I saw at the dealer shortly after buying the truck. The wire is a small gauge. If it is 18 gauge as I suspect and assuming the length is around 20 ft depending upon the current draw you could see voltage drops of over 30%. For a 15 amp load this means 12.67 VDC will be 8.84 volts (30%) at the other end. For a 1 amp reading it would be 12.41 (2%). With 16 gauge the drops would be 10.26 VDC and 12.51 VDC respectively and are still too low for charging a battery.

ifallsron

The converter in your camper draws from the truck power when you're hooked up and trickles into the battery.

If you have 7-pin, there's a dedicated pin.

You might get better information from you camper dealer than the truck dealer.

Simon

This is probably not what you want to hear,based on over10 years as a full timer in RVs you can't satisfactorily maintain a trailer battery with the tow vehicle. You need an outside power source. A small generator or solar panel. A small generator requires a 110 volt battery charger. A solar panel requires a controller. I would go with the solar panel because it works all the time during daylight hours and is more cost effective.

jkenprice1

That small wire is to charge the battery on the trailer braking system.

Mod (Ret.)

^^^ This ^^^

The 12V "accessory" wire that can be wired in on the round trailer connector is intended to operate a 12 volt accessory to the tow trailer. I use it on long hauls to operate the 12 volt refridgerator in my camper. On hauls longer than 2 hours, it will get the fridge cool enough to get the stuff out of the igloo cooler when we arrive at the camp site.

I doubt it will charge a battery well enough to keep it fully operational if its in use while its being charged by that lead/wire. And as mentioned, make sure that 12 volt wire is a sufficient gauge. It's traveling the length of the truck to the rear.