Unplug tow vehicle before plugging in shore power?

JohnD · Mar 22, 2015

Another topic thread got me thinking about something . . .

Is it better to unplug the trailer electrical from the tow vehicle before plugging in the trailer to shore power?

Or does it not matter . . . ?

I've always made sure that the truck and trailer were not plugged in to each other just to be on the safe side.

I've always thought that I might blow something otherwise!

branson4020 · Mar 22, 2015

I've never worried about it and never had a problem. On overnight stops where I'm not unhitching, I just leave the rig plugged into both the truck and shore power all night.

jnbhobe · Mar 22, 2015

It don't matter, they are two different circuits.

Jim.Allison · Mar 22, 2015

In a well maintained rig, your confidence can be high that nothing can happen. But you never know. If perhaps your charger fails, would you know it? Would you then be drawing off your 7 pin? Or perhaps your charger failed and your breakaway switch was engaged or "leaking current" and your brakes drained all your battery power. I would rather be trying to figure out why my house battery was dead rather than why all my batts (rig and TV) were dead.

IMHO, any trailer, not just RV's should be disconnected, its too easy to do. To risk killing your TV batts is not worth it. BTW, it is very detrimental to your batts to kill them, some cannot be recharged once they are completely drained, even if you can bring them back from dead the 100% discharge severely damages any battery, and your TV probably has 2 if it is a diesel.

Thankyou for presenting this question, because I too have never thought about this issue. I'm usually unhooked when stopped, but I could see a scenario where I might stop for the night and encounter an unexpected dead battery situation.

But this brings up the potential of inducing a problem by forgetting to plug in your 7 pin and getting a ticket for it, and/or dragging your 7 pin connector for 100 miles and having to replace it. Inducing a problem is as bad or worse than anything that might have happened in the first place. However I have seen red tags that you can hang on your rear view mirror that can remind you that you might have your TV antenna up, or any number of things. This might alert to a potentially induced problem, such as driving off with the 7 pin disconnected.

Good question. It might sound simple but upon examination, there is meat to it.

jsanders · Mar 22, 2015

The battery in the used 2011 Trail Runner was dry when I purchased it. When inquiring, a friend told me the converter can boil the acid/water mix from battery if battery is left connected without use for a long time. The travel trailer I purchased was not used last year by previous owner. Have any here heard of this happening?

Jim.Allison · Mar 22, 2015

Yes, did you replace the batt? How dry was it? Do not add acid only distilled water when attempting to charge or recover such a battery or any battery for that matter. The acid is still present only the water is gone. This primarily occurs when batteries are being heavily charged. Your charger/converter has no way of knowing that you batt is no good or it is just discharged, the more the batt becomes damaged the more the charger tries to charge it. Eventually the charger/converter applies more and more charge trying to charge the batt until the batt is dry. So yes it happens.

jsanders said:
The battery in the used 2011 Trail Runner was dry when I purchased it. When inquiring, a friend told me the converter can boil the acid/water mix from battery if battery is left connected without use for a long time. The travel trailer I purchased was not used last year by previous owner. Have any here heard of this happening?

jsanders · Mar 22, 2015

The battery that was in the travel trailer when purchased would not charge past 8-5 or 9.0 volts so I am using another battery that I have. I have not been camping this spring but so far that battery is holding a 12.8 volt charge after slow charging. I do have another question. I have that battery in travel trailer since charging about two weeks ago. The only 12 volt item that is on is my CD player. Do you know how much current it draws? Should I remove fuse or remove battery cable? I plan to go camping within a week.

Jim.Allison · Mar 22, 2015

I would put that under the category of parasites. The LP detector and a CD player display and a few other thing add to a lot of power when you look at the total picture. 24 hours per day, 7 days a week can deplete a batt in a hurry. .5 amps or 1 amp adds to 12-25 amp hours depletion per day actually less but that is another story. the upshot is, that un attended a batt can go dead in a matter of days. A maintainer is always called for. A small solar charger is the best way to maintain a batt and is a fairly inexpensive way to maintain one.

jsanders said:
The battery that was in the travel trailer when purchased would not charge past 8-5 or 9.0 volts so I am using another battery that I have. I have not been camping this spring but so far that battery is holding a 12.8 volt charge after slow charging. I do have another question. I have that battery in travel trailer since charging about two weeks ago. The only 12 volt item that is on is my CD player. Do you know how much current it draws? Should I remove fuse or remove battery cable? I plan to go camping within a week.

DocFather · Mar 22, 2015

Jim.Allison said:
In a well maintained rig, your confidence can be high that nothing can happen. But you never know. If perhaps your charger fails, would you know it? Would you then be drawing off your 7 pin? Or perhaps your charger failed and your breakaway switch was engaged or "leaking current" and your brakes drained all your battery power. I would rather be trying to figure out why my house battery was dead rather than why all my batts (rig and TV) were dead.

IMHO, any trailer, not just RV's should be disconnected, its too easy to do. To risk killing your TV batts is not worth it. BTW, it is very detrimental to your batts to kill them, some cannot be recharged once they are completely drained, even if you can bring them back from dead the 100% discharge severely damages any battery, and your TV probably has 2 if it is a diesel.

Thankyou for presenting this question, because I too have never thought about this issue. I'm usually unhooked when stopped, but I could see a scenario where I might stop for the night and encounter an unexpected dead battery situation.

But this brings up the potential of inducing a problem by forgetting to plug in your 7 pin and getting a ticket for it, and/or dragging your 7 pin connector for 100 miles and having to replace it. Inducing a problem is as bad or worse than anything that might have happened in the first place. However I have seen red tags that you can hang on your rear view mirror that can remind you that you might have your TV antenna up, or any number of things. This might alert to a potentially induced problem, such as driving off with the 7 pin disconnected.

Good question. It might sound simple but upon examination, there is meat to it.

Jim, I have RADD (Reading ADD) and when I see a post from you, I often think, "Oh crap, I will never make it through this lengthy post" - HA! HA! BUT, they are usually in my wheelhouse of understanding and I want you to know I appreciate all of your posts, long ones and shorter ones. Thanks

avvidclif · Mar 22, 2015

On the Ford TV when the key is off the power to the rv is turned off also. Can't run the battery down in the TV.

justafordguy · Mar 22, 2015

avvidclif said:
On the Ford TV when the key is off the power to the rv is turned off also. Can't run the battery down in the TV.

That's good to know, I was going to go check my F250.

jsanders · Mar 22, 2015

I found that was true too with my 2005 Silverado pickup.

Bob&Patty · Mar 23, 2015

Are you sure that there is no power at the 7 pin connector with the key off? Yes, you are not charging the battery but will your coach not "draw" current from your TV?? Ford did have a solenoid that only engaged to charge a coach battery when the key was on at one time.

Jim.Allison · Mar 23, 2015

DocFather said:
Jim, I have RADD (Reading ADD) and when I see a post from you, I often think, "Oh crap, I will never make it through this lengthy post" - HA! HA! BUT, they are usually in my wheelhouse of understanding and I want you to know I appreciate all of your posts, long ones and shorter ones. Thanks

Maybe its one "ADD" to another and you are the only one that can understand what I write. Maybe that is why it is in your wheelhouse.

Bob&Patty · Mar 23, 2015

Must be in my wheelhouse also as I do understand him. Jim must have been an attorney in another life or have one heck of a spell check.

travelin2 · Mar 23, 2015

JohnD said:
Another topic thread got me thinking about something . . .

Is it better to unplug the trailer electrical from the tow vehicle before plugging in the trailer to shore power?

Or does it not matter . . . ?

I've always made sure that the truck and trailer were not plugged in to each other just to be on the safe side.

I've always thought that I might blow something otherwise!

jnbhobe said:
It don't matter, they are two different circuits.

Asked the same question at an electronics seminar at an RV dealer last fall.
Jon's answer was the reply.
No reason to disconnect the TV. Shore power will not effect on the TV.

Sent from my iPhone using Tapatalk

Jim.Allison · Mar 23, 2015

Bob&Patty said:
Must be in my wheelhouse also as I do understand him. Jim must have been an attorney in another life or have one heck of a spell check.

That is an astute observation, I have only written about 5000 prosecution reports when presenting federal cases to the Assistant US Attorney. But like anyone else I can and do get lazy in grammar and spelling. I can't forget my supervisors red ink on my reports. I worked for years to perfect my reports to avoid all the red circles, which is particularly difficult to do when many of the corrections were demanded from a supervisor that knew squat about spelling and grammar. I think clarity is important.

I was searching the forum the other day for a solution to a problem, and I found a response from me in the thread. Either it was moved there, or I did not understand the thread, because my post had nothing to do with the subject. LOL, that is ADD at its finest.

Bob&Patty · Mar 23, 2015

I object...unresponsive, irrelativent. and not germain to this hearing. Sorry, watched to many Perry Mason and Mattlock programs. LOL Jim, I have always liked the law and wish I had persued it when I was younger. Thought about going back to school and at least become a para-legal....but at almost 70 might be wishful thinking.

Jim.Allison · Mar 23, 2015

Me too, but I could barely get through college at that age much less study law. I was a grown man before I could truly sit down and study. Matlock/Mason fan also.

Bob&Patty said:
I object...unresponsive, irrelativent. and not germain to this hearing. Sorry, watched to many Perry Mason and Mattlock programs. LOL Jim, I have always liked the law and wish I had persued it when I was younger. Thought about going back to school and at least become a para-legal....but at almost 70 might be wishful thinking.

JohnD · Mar 23, 2015

I think I will continue to unplug the truck before plugging in shore power . . . just to be on the safe side!

I also don't think that I would take off without plugging the trailer back into the truck as I always do a trailer brake test and light check before we hit the road.

Unplug tow vehicle before plugging in shore power?

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