Duramax batteries drained by camper while plugged in.

[smitty81503]

I’ve had my GMC duramax parked for two days with my truck camper plugged in to the
the house. I’ve been running the refrigerator in the camper . Now my two truck batteries only show about 10.4 volts and wont crank the engine. Any ideas what could be causing the discharge on the truck batteries? I have 2 six volt batteries in series for the camper itself.

[wnjj]

Sjm9911 wrote:
Why would he have the fridge on 12v when hes plugged in to the house?

Same reason the batteries are dead. The 120V or the converter clearly wasn't working. If not the fridge, there's really nothing else that should pull down multiple batteries in only a couple days.

[Sjm9911]

Why would he have the fridge on 12v when hes plugged in to the house?

[wnjj]

KD4UPL wrote:
GM trucks have nothing to disconnect the camper batteries from the truck batteries. They are constantly hooked together as long as the 7 pin plug from the camper is plugged into the trailer. The solution is to unplug the cord from the truck when dry camping. Or, you can install a switch in the charge line and turn that off. If you want to automate the process I would install an automatic charge relay from Blue Sea systems or another reputable brand.

May not be possible to disconnect the cord with the truck camper loaded. Another solution is to pull the stud #1 fuse in the under hood fuse box.

However in this case, clearly the converter isn’t working and the truck and camper batteries were powering the fridge, I’m assuming in 12V mode since they died so quickly.

[2oldman]

Sjm9911 wrote:
Also check you batteries, they could just be going bad?

If they're OEM, absolutely. Profile shows a 2003

[ktmrfs]

KD4UPL wrote:
GM trucks have nothing to disconnect the camper batteries from the truck batteries. They are constantly hooked together as long as the 7 pin plug from the camper is plugged into the trailer. The solution is to unplug the cord from the truck when dry camping. Or, you can install a switch in the charge line and turn that off. If you want to automate the process I would install an automatic charge relay from Blue Sea systems or another reputable brand.

yup, Cleary described in the truck owners manual. However I believe it is not all trucks, It is the diesel trucks or gas w/o the aux battery. IIRC dual battery gas trucks disconnect when the ignition is off.

[wa8yxm]

You had the truck camper plugged into the house:

Well. Most trailers and motor homes have a device called a Converter. This "Converts" 120vac to battery voltage... I do not know if a "Truck camper" has one of these or not.. if not you may wish to add one I recommend a Progressive Dynamics 9200 most likely the 9245 or 9260 depending on your batteries (Total the C-20 amp hour capacity of yoru batteies and multiply by 0.3 that's the last 2 digits of the model number you wish to match)

Get a "P" model (plugs in, though you may need an adapter since some of them come with 20 amp plugs. ) or request a 15 amp plug.

[Sjm9911]

Also check you batteries, they could just be going bad?

[schlep1967]

Does your truck camper have a converter/battery charger in it? If it does, my guess is it isn't working. The refer should be running off the 12 volt and the converter should be supplying enough to do that when plugged in to shore power without pulling from the truck.

[KD4UPL]

GM trucks have nothing to disconnect the camper batteries from the truck batteries. They are constantly hooked together as long as the 7 pin plug from the camper is plugged into the trailer. The solution is to unplug the cord from the truck when dry camping. Or, you can install a switch in the charge line and turn that off. If you want to automate the process I would install an automatic charge relay from Blue Sea systems or another reputable brand.