PChouinard

Should a tow vehicle have a deep cycle battery if it is pulling a fifth wheel rv with a deep cycle? My friend is looking into this setup and I was wondering if paralleling a cranking batt with a deep cycle will have any effect on the batts.Any input?

RustyJC

No. The services are totally different. A tow vehicle (let's say my truck) needs a battery that can provide high current for short durations for cold starting. A deep cycle RV battery must provide lower currents for long durations and be tolerant of deep levels of discharge and subsequent recharges. Different horses for different courses.

Rusty

PChouinard

I know the differences between the two. What I want to know is; Should the trailer be unplugged from the truck while parked i.e. camping, parking over night etc? Are the two batts compatible to be connected in parallel? I know it is fine while the engine is running and the alt is producing power.

RustyJC

The original question was "Should a tow vehicle have a deep cycle battery if it is pulling a fifth wheel rv with a deep cycle?" That's what I answered.

Yes, the truck should be unplugged from the RV while camping, parking overnight, etc. This is simply to ensure that the RV doesn't discharge the truck battery if it's not plugged in to shore power or if the RV's power converter fails. Alternately, one can install a battery isolator that breaks the +12VDC lead to the 7-pin connector when the truck's ignition is turned off.

Rusty

PChouinard

Thanks Rusty for the replies. I agree and that's what I was advising my boss to do. The isolator is a good idea but my boss is too big of a pig farmer to do that. He said he'll just unplug it. Thanks again..

cditrani

Do a google search on "RV battery isolator". There are devices specifically for this propose. Allows the batteries in the RV to charge when the truck engine is running and be isolated from the truck when the engine is off.

Batteries of different designs can be mixed but it's not a good idea. In fact you should avoid connecting any batteries together unless they are new (when you first connect them) and the same make/model. Mixing old and new batteries can shorten the (remaining) life of both, similarly for batteries of different spec.

RustyJC

I agree - as long as we're talking about matching RV deep cycle batteries (6V or 12V) or truck starting batteries. It's not necessary (or even desirable) to match RV and truck batteries to each other, however.

Rusty

Hvytrkmech

Most newer tow vehicles (any brand) have the trailer hot feed relayed, and if the ignition is in the off position there is no power to the feed line.

RustyJC

When did Dodge start providing this feature? None of mine have ever had it.

Rusty

Hvytrkmech

Not sure when Dodge started, my 06 does not have power with the key off. I found that out when installing the plug in the bed for my 5ver. As far as Ford, since 99, and as far as Chevy, 01 and up for the diesel tow package.

XLR8R

Hmm - my '05 still has the 12V pin in the 7-pin harness hot at all times...

RustyJC

Wasn't it 2006 when Dodge introduced its whiz-bang computer gizmo that controls trailer lights, etc. in lieu of fuses? It sounds like this change may have been part of that.

Rusty

Hvytrkmech

At first I thought so, but after taking a test light to it this morning I found I had no power either way. I found a wire had pulled partially pulled out of a shrink wrap connection that I had used, my own fault. After checking everything else I found that the trailer feed is hot all the time so I apologize for the mis information on the Dodge, I came to Dodge from Ford so I'm learning as I go. Thank you for pointing me in the proper direction.

01RAMer

Sounds like we're back to the RV Battery Isolator.

XLR8R

Rusty's right, though - 2006 incorporated changes in the trailer circuit protection wiring scheme... supposed to be a real PITA if you overload it with extra lights, etc.