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7 Pin Round Trailer Plug Wiring Reconfigure for 12V+ Engine On

12V Round Pin RV Plug Ram

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#1 OregonOzzy

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Posted 03 August 2020 - 08:54 PM

Hello all,

Trying to get a Renogy DC-DC battery charger configured in my Hawk. This Renogy requires a 12V+ feed for sense (I know there are others that do not require this - well too late for that). 

I was kind of surprised to find out that the 7-pin round trailer plug at the hitch has an "always on" 12V+ feed. It is NOT switched. Constant 12V+ whether ignition is on/off/acc. Confirmed via actual testing and literature. So, do any of you smart people out there know of a way to make this always on feed at the 7-pin trailer plug be active only when switched (engine running)? Don't want to run another wire all the way back from fuse box to the trailer plug. I already have 4g wires terminating at the back bumper in an Anderson power plug in this truck. I have seen documentation to switch the internal power outlets from acc-on to always-on just by swapping some fuses. I am hoping that there is something simple like that. The truck is a 2016 RAM 2500. I could tap into the tail lights and get the 12V+ but it kind of defeats the purpose of only getting power with engine on. Thanks in advance......Ozzy


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2000 Alaskan 10' CO

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#2 lmwilco1

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Posted 04 August 2020 - 06:28 PM

There two different sense options, one for the alternator and one for the camper battery. I assume you have a smart alternator and that is what you are trying to wire up using the ignitions sense Input. It needs to go to an ignition switches source so the dc to dc charger know when to draw from the vehicle battery/alternator. So the feed from the 7 pin connector will not work if it is hot all of the time. If you are referring to the battery voltage sense that would connect directly to the battery that you are charging with the dc to dc charger as you could see a voltage drop across the charging cables and you could overcharge. The battery sense input eliminates the voltage drop so you get the correct battery voltage to the charger. 


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#3 OregonOzzy

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Posted 04 August 2020 - 06:40 PM

Hi Imwilco1, thank you for your response. Yep, you have it right, it is the ignition sense input for the Renogy DC-DC charger. They call it it "D+". The DC-DC charger waits to get a 12V+ here before starting up and doing its job. Some people have just connected it with a switch to an always on circuit and "remember" to switch it on/off. I am trying not to rely on my memory too much. :-) and make it more fool proof.

The voltage drop from the truck battery to the DC-DC charger has been pretty much eliminated with 4G wires (30A fuses+Anderson pole connector) - which was probably an overkill - since the DC-DC is supposed to compensate for that and I could have gone with a less heavier gauge of wire. But now I can also run a small winch in the back off that Anderson connector when needed (a plus). 


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2000 Alaskan 10' CO

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#4 Vic Harder

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Posted 04 August 2020 - 08:09 PM

Hello all,
Trying to get a Renogy DC-DC battery charger configured in my Hawk. This Renogy requires a 12V+ feed for sense (I know there are others that do not require this - well too late for that).
I was kind of surprised to find out that the 7-pin round trailer plug at the hitch has an "always on" 12V+ feed. It is NOT switched. Constant 12V+ whether ignition is on/off/acc. Confirmed via actual testing and literature. So, do any of you smart people out there know of a way to make this always on feed at the 7-pin trailer plug be active only when switched (engine running)? Don't want to run another wire all the way back from fuse box to the trailer plug. I already have 4g wires terminating at the back bumper in an Anderson power plug in this truck. I have seen documentation to switch the internal power outlets from acc-on to always-on just by swapping some fuses. I am hoping that there is something simple like that. The truck is a 2016 RAM 2500. I could tap into the tail lights and get the 12V+ but it kind of defeats the purpose of only getting power with engine on. Thanks in advance......Ozzy

That plug is not supposed to have an always on terminal according to the stuff I’ve read https://www.google.c...=ITg5sSJTCVsygM

So I’d look at wiring it up correctly.


Edited by Vic Harder, 08 August 2020 - 03:15 AM.

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#5 OregonOzzy

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Posted 08 August 2020 - 01:17 AM

Stock wiring and factory hitch. No modifications have been made. If any were made, then of course I would have looked at them first. Sometimes Google is not the best information.
To save someone else the trouble, you can easily confirm the details of as shipped options directly from FCAGroup using their customer support (providing your VIN info). They were very helpful and provided response within 1 business day on all my queries.
Below is the actual email regarding this, so make sure to check your power plugs before a "surprise" dead truck battery if you leave it connected to the camper. Others have noted similar on FCA forums.....

 

From FCA Group Customer Service:

 

Thank you for contacting FCA US LLC.


Our records indicate this vehicle was equipped from the factory with the following:
XFK 7-Pin Wiring Harness

According to available information, the 12V+ pin (battery pin) on the vehicle's 7-pin trailer connector is operating as designed. If a recreational vehicle is connected to the vehicle's 7-pin trailer connector, power can be drawn from the vehicle's battery.  

FCA US LLC does not recommend modifying or altering any vehicle from the original manufacturer's specifications; therefore, we are unable to assist you with your vehicle modification or alteration request.


Edited by OregonOzzy, 08 August 2020 - 01:18 AM.

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2000 Alaskan 10' CO

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#6 Vic Harder

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Posted 08 August 2020 - 03:15 AM

OK, so it is wired as it should be from the factory.  Maybe that is not the way you want it to be wired?


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#7 ntsqd

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Posted 16 August 2020 - 12:15 AM

I would look at how that wiring is added to the base truck's wiring loom. If there is an opportunity on the 12VDC+ wire to interrupt it with an IGN switched relay or contactor I would do so at the connector in a way that is easily reversed.

 

Backing up though, the charger needs this as a trigger voltage or as a supply voltage?


Edited by ntsqd, 16 August 2020 - 12:15 AM.

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#8 OregonOzzy

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Posted 21 August 2020 - 11:41 PM

ntsqd, sorry for the late reply. Busy enjoying the new set-up and what is left of summer in Oregon. That 12v+ is only for the trigger voltage (Renogy DC-DC chargers need this extra wire). I left the truck wiring as-is for now mostly and just used the 7pin for now with an always-on and interrupted it with a simple toggle switch. I usually end up upgrading trucks every few years, so did not want to get too creative with wiring on it. 

I have posted my detailed solution at: https://oregonozzy.b...d-humble-3.html


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2000 Alaskan 10' CO

2018 F-350 Extended Cab 8'

 

 

 






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