Plugged in or not?

[John_Joey]

I'm sure this has been asked before, but we're leaving shortly and I don't have time to do a real search.

I've had other RV's never a truck/5'ver combo. When I went out this morning I noticed that the brake controller light was green. I was plugged into the trailer plus 110V.

So the question is what is the "best practice" here. Do you always stay connected to the truck when you're not moving. Do you unconnected when only hooked to shore power, or doesn't it matter because there are safe guards built into the system?

Thanks

[Lantley]

Always unplug. It's too easy to do and foolproof. All other methods are counting on circuitry to protect you. Something can fail and create a problem.
Worst case scenario is some kind of weird computer problem is created due to a backfeeding circuit
Unplugging is always foolproof

[CarlT100]

Thankfully, my Ford is isolated. I do not bother to unplug the camper when I have the camper plugged to shore power.

[rskeans]

FWIW - - I have a '14 RAM and it is not isolated. The truck battery goes directly to the 5ver through a 30A fuse in the RAM distribution box and in our case another 30A fuse in our 5ver via the 7 pin.

[RustyJC]

Allworth wrote:
Dodge - who knows? Test it. Connect a 12V test light between 11 o'clock and 5 o'clock on the truck outlet (facing the truck) with the switch off. If it lights up, no isolation. If dark then isolated.

Based on my experience, I'd put Dodge/Ram into the "not isolated" category as well. I've towed 5th wheels with 1996, 2002 and 2011 Ram 3500 duallies, and none have had battery isolators. Pin #4 in the Pollak 7-blade connectors has always been hot on the truck side, ignition on or not.

When we're staying overnight and not unhitching the truck, I'll generally leave the truck plugged to the trailer when we're on shore power. In effect, the truck batteries are in parallel with the RV batteries so are being charged off the RV's power converter just like 2 more batteries in the RV's battery bank. I've had multiple Todd Engineering converters fail way back when (I've never lost a Progressive Dynamics which is what I've had since 2000), but I've always had them fail "dead" - never trying to feed 120VAC into the 12VDC side. Could it happen? I suppose it might, theoretically, but so could a direct meteor strike on the 5th wheel while we're sleeping in it. It's not something I spend time worrying about.

Rusty

[Sturgeon-Phish]

enblethen wrote:
Back feeding into the trucks computerized systems is what I would be concerned about and not draining the battery.

This is my reason to disconnect as GMs do not isolate, and campground power systems can be a problem

[John_Joey]

THANKS EVERYONE!!! Thinking "best practice" is to unplug when appropriate with my rig till I have the time with my meter to check things out.

Not new to RV'ing, but new to doing it this way. Had a good pull today, not so good at backing it up, and currently trying to get the furnace running (got heaters:B.) Which means my time can now be spent figuring that one out, and not spending time searching whether I should unplug or not. 🙂

[Allworth]

Ford - isolated

GM/Chevy - not isolated

Dodge - who knows? Test it. Connect a 12V test light between 11 o'clock and 5 o'clock on the truck outlet (facing the truck) with the switch off. If it lights up, no isolation. If dark then isolated.

[enblethen]

Back feeding into the trucks computerized systems is what I would be concerned about and not draining the battery.

[laknox]

IMO, it would take days to run down the truck's battery(ies) enough to cause starting issues, unless you're heavy battery users. For 24 hours, I wouldn't worry too much about it, that's for sure, at least with "normal" battery usage. As far as plugging into a pedestal, yes, I unplug the truck before doing so.

Lyle

[tcamper]

I'm just funny like that .... and worry there might be a bug, or short or spike somewhere .... so I always unplug from my truck when we stop and plug into shore power.
I figure why take the chance, and it is a very simple task to unplug when you arrive and re-plug when you leave.

Note: when I unplug I lay the cord over the tailgate or bed rail so I don't forget to re-plug.

[BB_TX]

If we are overnighting and not unhooking the 5er, cord stays connected to the truck and is also connected to shore power (2012 F350 and previous 2007 F350).

[W6GPM]

Doesn't your truck have a relay between the battery and trailer connection? My old Ford has one so no problem leaving the trailer plugged in as long as the ignition switch is off. Easy to check to see if your truck has it.

[enblethen]

Sounds like you have a back feed into TV.
I would check to see if your TV has an isolation relay to prevent running down TV battery.
Fords have a relay, some Dodges have relays, GMs do not and should have one installed. Something like this style and installation
Battery switch

[bpounds]

What you can safely do depends on your truck.

My '06 Ford has an isolation relay, and if the truck is not running, the RV battery is isolated from the truck. The RV cannot run down the truck battery. But if I start the truck, there is a connection between RV battery, truck battery, alternator, and if I was plugged into short power, the linkage would include the RV converter. I consider that risky, so I would do not do that.

I was with a friend when his RV depleted his truck battery overnight. It was a popup with a 3-way fridge, and it ran on 12VDC all night. It was a Chevy from about the 2000 model year, and that model did not isolate.

So you have to know how your truck works, but the safest practice is to not connect to shore power and truck power at the same time. The computers and electronics in new trucks is just too complex and expensive to take unnecessary risk.