Disconnect 7-PIN for charging

[gargabri80]

Okay, here is my question. I have a 2007 F350 and a Truck Camper, so I have the pigtail plugged in all the time.
I am completely rewiring the camper found this 12v wire that is always hot and traced it back to the Accessory power from the 7 pin.
I'm worried that the camper and the camper battery (new LiFePo4) will discharge my Truck battery if I don't drive it much.
Am I right to be concerned? And a follow-up question is if I'm on shore power, with my camper's battery charger charge my truck battery?

 

[John Frum]

Am I right to be concerned?

Yes.

 

[Zwy]

Okay, here is my question. I have a 2007 F350 and a Truck Camper, so I have the pigtail plugged in all the time.
I am completely rewiring the camper found this 12v wire that is always hot and traced it back to the Accessory power from the 7 pin.
I'm worried that the camper and the camper battery (new LiFePo4) will discharge my Truck battery if I don't drive it much.

If you leave the 7 pin plugged in, eventually the 2 batteries will be even voltage. If you have loads on in the camper, then yes, you will drain the truck starting battery. The solution? Either unplug the 7 pin when parked for extended periods or install a switch.

Am I right to be concerned? And a follow-up question is if I'm on shore power, with my camper's battery charger charge my truck battery?

It will to a point due to resistance in the circuit. A long enough time frame it will completely charge it thru the 7 pin.

What type of battery in the camper?

 

[HRTKD]

If the 7 pin is always hot, that's a problem. Bug or feature? I don't know, but I posed the question to the eggheads on the Ford Truck forum to see what they had to say. Maybe it's not supposed to be that way from the factory. I know my 2017 F-350 doesn't work that way.

 

[Zwy]

If the 7 pin is always hot, that's a problem Bug or feature? I don't know, but I posed the question to the eggheads on the Ford Truck forum to see what they had to say. Maybe it's not supposed to be that way from the factory. I know my 2017 F-350 doesn't work that way.

Some run a keyed ignition relay but for 2007 Ford I think it was hot all the time. People have something like a horse trailer and want to have a few lights at night. So the pin is hot.

A relay can be wired in easy enough where it will be controlled off the ignition switch.

 

[brb58]

If the 7 pin is always hot, that's a problem. Bug or feature? I don't know, but I posed the question to the eggheads on the Ford Truck forum to see what they had to say. Maybe it's not supposed to be that way from the factory. I know my 2017 F-350 doesn't work that way.

That's because they have a trailering module now that controls the 12V to the 7 pin connector.

 

[HRTKD]

A guy on the Ford Truck forum that works on RV's for a living said that the 2007 F-350 shouldn't be live without the ignition on. His 2002 isn't live.

Maybe a prior owner bypassed the trailer module?

 

[brb58]

A guy on the Ford Truck forum that works on RV's for a living said that the 2007 F-350 shouldn't be live without the ignition on. His 2002 isn't live.

Maybe a prior owner bypassed the trailer module?

Assuming a 2007 has a trailer module. Your 2017 definitely does.

 

[time2roll]

AFAIK all F150/F250/F350 have an isolation relay for at least the last 25+ years. Need to see if there is a fault or modification and get it set back to working like original.

 

[chrisski]

I have a 2005 Ford F250 DIesel 6.0. They were made from 2003-2007. 2002 and prior the diesel was a 6.4. 2008-2011 was a 6.4 diesel, then came the 5,7.

Whether or not the 12 volt is live all the time is of no concern to me about leaving it parked all the time. Plenty of solar to charge the truck battery if that’s what’s needed.

What was of concern to me is my 24 volt to 12 volt DC to DC converter was hooked to the RV 12 volt side. I never disconnected this 12 volt wire front he truck 7 pin to my battery. I was wondering if my RV would pull a charge backwards through the Truck Battery to converter and then 24 volts. I checked it a few times to see if the converter got warm and it did not. This Victron product was lacking on documentation. Only about a quarter page in English to say how to set up and not much for specs.

Most of the time when I take the RV out now, I am in it for a couple of nights and do not disconnect anything from the bed of the truck. Next time I go, I will monitor whether it is back feeding into the truck. Should be pretty easy. The DC to DC converter is set to an even 13.6, so if this trailer 7 pin is hot with the ignition off, the battery would read 13.6 volts, minus some for DC loss. If the pins aren‘t hot, I’ll get the resting voltage of the battery at Mid to high 12s Volts.

My RV is almost completely charged when I drive it, and I see the normal 12.9 - 13.3 for my alternator, not any increase when it could be pulling from the RV battery.

 

[gelmjw]

How about a VSR in-line with the 7-pin? When either side is charging, the connection is on, otherwise if neither side is charging the connection is off.
VSRs

 

[brb58]

How about a VSR in-line with the 7-pin? When either side is charging, the connection is on, otherwise if neither side is charging the connection is off.
VSRs

Can't use that with an LiFePO4 battery. The VSR could stay on for a long time just due to the lithium battery voltage until it discharged enough into the lead acid battery in the vehicle.

 

[time2roll]

How about a VSR in-line with the 7-pin? When either side is charging, the connection is on, otherwise if neither side is charging the connection is off.
VSRs

I use a Trik-L-Start combiner to jump over my Ford relay and allow the trailer that has solar to maintain the truck start battery while in storage.

 

[HRTKD]

I use a Trik-L-Start combiner to jump over my Ford relay and allow the trailer that has solar to maintain the truck start battery while in storage.

My F-350 is a garage queen. It was bought to tow and that's pretty much all it does unless it's a load of gravel or lumber. When it's in the garage I have it hooked up to a NOCO battery maintainer. My wife makes fun of my sissy truck not being outside like a tough truck. But these newer trucks are theft magnets and her Hyundai isn't.

Getting the 7 pin to start the charge is almost a challenge with these newer trucks. There is a video that a guy did showing all the steps he had to go through to get the charge started without actually driving the truck.

 

[time2roll]

My tough truck has a cab forward sissy cover on to keep it warm in winter and cool in summer while outside

I think a jumper could replace the relay to get full time power if desired.

 

[HRTKD]

On the 2007 model year, check relay 301 in the power distribution box.

It's a longshot, but the relay may be frozen closed, allowing power to the 7 pin all the time.

 

[Ranger Rick]

Just don't want the complexity and I will not run a dedicated wire from the alternator anyway. So would rather spend money on getting solar if there is a need.

And save money by not having to replace your truck’s alternator. Lithium ion batteries can overwork the alternation ?

 

[HRTKD]

@gargabri80 , what did you figure out with your 12 volt power source?