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Desire 7-pin trailer connector charging pin off when engine stopped

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LoopyLyle

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Hi, I have a 2019 3500 DRW truck. My slide-in camper plugs into the 7-pin trailer connector at the rear of the bed. For purposes of charging my campers batteries when driving, I would like to use charging pin #4 as a trigger to a dc-dc charger to turn on when the engine is running. Problem is that pin 4 *always* shows 12 volts even when the engine is stopped. Is there a setting, configuration or modification that will make the charging pin #4 active *only* when the engine is started?

Thanks in advance for any help!

Cheers, Dwight Fromm
 
LoopyLyle said:
Hi, I have a 2019 3500 DRW truck. My slide-in camper plugs into the 7-pin trailer connector at the rear of the bed. For purposes of charging my campers batteries when driving, I would like to use charging pin #4 as a trigger to a dc-dc charger to turn on when the engine is running. Problem is that pin 4 *always* shows 12 volts even when the engine is stopped. Is there a setting, configuration or modification that will make the charging pin #4 active *only* when the engine is started?

Thanks in advance for any help!

Cheers, Dwight Fromm
Click to expand...
Why not just use the positive pin to charge the batts no need for a charger thats how most trailers run it .... you could also use the running lights as the trigger just turn the lights on during the day while driving aswell....
 
H3LZSN1P3R said:
Why not just use the positive pin to charge the batts no need for a charger thats how most trailers run it .... you could also use the running lights as the trigger just turn the lights on during the day while driving aswell....
Click to expand...
This.

Use a relay to pass Pin#4 power and trigger it with the running lights or an Aux switch.
 
For anyone who dry camps the mod would be good for pull trailers and 5th wheels as well.
When I dry camp and don't disconnect/unhook my trailer.I always pull the 7 pin plug
Have seen too many, including myself, who don't unhook their trailer, don't pull the 7 pin and a week or so later they have a dead truck starting battery.
 
Brutal_HO said:
Use a relay to pass Pin#4 power and trigger it with the running lights or an Aux switch.
Click to expand...
Brutal,
That's the best way. I would intercept the Pin 4 12v wire at the fuse box. However, when I look at the manual's fuses I don't see a fuse for that 12v wire. It has to be fused. Did I miss something? Do you know what fuse?

Another idea is to wire pin 4 fuse slot direct to an Aux switch and make the Aux switch ignition only
 
John Jensen said:
Brutal,
That's the best way. I would intercept the Pin 4 12v wire at the fuse box. However, when I look at the manual's fuses I don't see a fuse for that 12v wire. It has to be fused. Did I miss something? Do you know what fuse?

Another idea is to wire pin 4 fuse slot direct to an Aux switch and make the Aux switch ignition only
Click to expand...
Thanks for all the replies so far! Here are some additional details to answer some of the questions raised:

o I need a dc-dc charger to pass voltage regulated to 14.4 volts @ 60 amps of current to charge a 480ah lithium battery bank. The usual trailer connector charge line is not up to this task.
o I am already using the running lights to trigger another function
o What do you all mean by "aux" switches? Up-fitter switches? If so, I don't have them. And from what I read here in the forms they can not be added post-build for my 2019 3500.

I like the idea of plugging a line into the fuse socket for the charging pin connected to a relay triggered by ignition voltage. Does such a gadget exist?

Thanks again for the suggestions. I really would like to get this functionality enabled to head off chances of running my truck batteries dead.

Cheers, Dwight
 
LoopyLyle said:
Thanks for all the replies so far! Here are some additional details to answer some of the questions raised:

o I need a dc-dc charger to pass voltage regulated to 14.4 volts @ 60 amps of current to charge a 480ah lithium battery bank. The usual trailer connector charge line is not up to this task.
o I am already using the running lights to trigger another function
o What do you all mean by "aux" switches? Up-fitter switches? If so, I don't have them. And from what I read here in the forms they can not be added post-build for my 2019 3500.

I like the idea of plugging a line into the fuse socket for the charging pin connected to a relay triggered by ignition voltage. Does such a gadget exist?

Thanks again for the suggestions. I really would like to get this functionality enabled to head off chances of running my truck batteries dead.

Cheers, Dwight
Click to expand...
You can always just use a relay to trigger the #4 pin to an ignition source
 
H3LZSN1P3R said:
You can always just use a relay to trigger the #4 pin to an ignition source
Click to expand...

Sorry, I guess I'm missing something.Exactly how do I configure triggering pin4 with a relay? How would I intercept the pin4 wiring to add that relay? Is there a gizmo I need to get to plug into the fuse or port similar. Any experience/advice appreciated.

Thanks, Dwight
 
Inserting this device in your battery positive line somewhere between your battery and the trailer plug would likely work. you would have to find out which wire it is in the harness to the trailer plug. It senses the increased voltage when your alternator is charging and connects the two large terminals together. They use them on motorhomes to connect the house and chassis banks together for charging but disconnect the two banks when there is no charging source. Basically you are doing the same thing. There are others out there but Victron makes good quality stuff.

 
LoopyLyle said:
Sorry, I guess I'm missing something.Exactly how do I configure triggering pin4 with a relay? How would I intercept the pin4 wiring to add that relay? Is there a gizmo I need to get to plug into the fuse or port similar. Any experience/advice appreciated.

Thanks, Dwight
Click to expand...
Find the wiring coming out of the fuse box i don't have the diagram to say what wire it is but yes just a standard relay that is rated at 30 amp and you can get an ignition hot from the fusebox as well
 
Casey B said:
Inserting this device in your battery positive line somewhere between your battery and the trailer plug would likely work. you would have to find out which wire it is in the harness to the trailer plug. It senses the increased voltage when your alternator is charging and connects the two large terminals together. They use them on motorhomes to connect the house and chassis banks together for charging but disconnect the two banks when there is no charging source. Basically you are doing the same thing. There are others out there but Victron makes good quality stuff.

Click to expand...
Yes! Perfect! This does exactly what I want. I'll be inserting this between the pin4 charging standoff stud on my camper and the 12-volt trigger port of my dc-dc charger. Now I won't have to mess around mod'ing anything under the hood! :) The array of these types of electrical gadgets VIctron makes is truly amazing. Amazon will be delivering this part to me on Sat.

Thanks everyone for your replies and especially to CaseyB for this super suggestion!

Cheers, Dwight
 
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