12 volt system - Okanagan UDB

Hi folks!

I admit I'm suffering from information overload with respect to my campers 12 volt system! :)

So I'll start slow with a couple questions...

Currently (no pun intended) my camper is outfitted with one 12 volt battery and a solar panel. I don't have the model numbers and capacities handy just yet.

During our inaugural camping trip I made several observations that lead me to believe the camper is operating from the truck batteries (diesel truck with 2 batteries):
1/ the solar meter in the TC is measuring 11 volts (low I think)
2/ the negative terminal at the TC battery was disconnected
3/ when connected to the 7 way harness the slide out and happijacks operate very well. when disconnected to the 7 way the slide out struggles to move and the happijacks do not work at all.

This has me a little concerned for various reasons.
First, I'm worried I may inadvertently discharge my truck batteries and leave us stranded.
Secondly, I don't want to shorten the life of my truck batteries by misusing them for the TC.

My first thought is to remove the fuse from the truck that supplies power to the 12 volt pin on the 7 way harness.

With the little reading I've done, I understand the 12 volt system can be easily damaged without proper maintenance, while avoiding misuse. My thinking is, I'll start isolating the truck power from the TC power and go from there.

By the way, the TC is connected to a 7 way receptacle I installed in the truck box. I can't access it when the camper is loaded. Thus my idea to simply remove the fuse.

Perhaps the TC battery is shot.
I'm a complete newby when it comes to 12 volt systems. I would appreciate any advice you can offer me. For instance, I'm not entirely certain how to go about testing the TC battery after I have it isolated from the Truck. I don't know what the solar panel contributes to the system insofar as testing and measuring is concerned.

Thanks in advance!

Truck Campers

Duramaximos
Explorer
May 20, 2014
Hi everyone,
I disconnected the battery and took the following pics....

NOTE, the battery was completely disconnected and the power slide worked well. That tells me the TC is drawing power from the truck.
The pictures of the Solar regulator panel were taken with the TC battery removed, but the TC connected to the truck via the 7 way harness.

My boat battery is still in storage and I know it is good so I tested it as well. It measured 14.1 volts. This isn't right, is it?! I thought batteries with no load should measure about 12.7 volts.

I'm scratching my head here.
Tamnative
Explorer
May 20, 2014
Duramaximos wrote:
I have another newbie question. Since I don't have a test light, can I use my multimeter to test for power at the 7 way receptacle?

I'd like to confirm if I have power at the 7 way with the truck in the off position.

Yes you can
Duramaximos
Explorer
May 20, 2014
I have another newbie question. Since I don't have a test light, can I use my multimeter to test for power at the 7 way receptacle?

I'd like to confirm if I have power at the 7 way with the truck in the off position.
Duramaximos
Explorer
May 20, 2014
Boatycall wrote:
Well, first, welcome.

We need to know what kind of truck you have. Guessing from your screen name, a Chevy. FYI, if you could, fill out your Signature in "preferences". But regardless, the 12v accessory pin is NOT supposed to be energized when the truck is off. There may be something mis-wired in your 7-pin.

And yes, at 11v, you either have one very low on water, or you need a new battery. I (like many others here) would recommend 2 golf cart batteries rather than RV Deep Cycle.

My truck truck is a 2012 GMC 3500.

This video suggests the 7 pin is energized with the truck off...but perhaps he has the key in the on position.
https://www.youtube.com/watch?v=Xb-X5uAwht0

I do have a multi-meter so I will take some measurements and report back.

Thanks.
AnEv942
Nomad
May 20, 2014
Wonder why T/C battery was disconnected? It cannot recieve charge from truck when running-you do need to address that-isolate the truck from TC. Truck should send charge to camper while running but camper shouldnt be able to draw from truck when key off. Several simple ways to do that- but first need to identfy whats what.

Yes 11 volts is pretty dang low-bad low, unless the solar is directly connected Im not quite sure how its even reading battery? Not knowing output or size of solar hard to say why its so low, unless cable has been off for some time, wouldnt be receiving charge from truck or converter. A simple multi meter (or take battery somewhere)to test. Check water and charge or have charged, unconnected or out of camper.
Neg cable off, obviously camper not drawing from it-nothing able to charge it -odd. Was this just picked up? Maybe PO pulled cable so camper parasitic loads didnt drain? But the cable should be hooked up to battery.

The slide and more so the jacks need a really good source of power, Ill only operate either while truck is running. Im surprised the jacks worked at all with TC battery disconnected, though that depends how they are wired. What you have now by description IS camper using truck batteries. Got some puzzles.
cewillis
Explorer
May 19, 2014
Duramaximos wrote:

2/ the negative terminal at the TC battery was disconnected

If you mean noting is connected to the battery negative, than the battery is not doing anything.
Test the battery, and if OK -- reconnect.
You need something to isolate the truck batteries when the engine is off. Also, the 7-pin connector wiring is inadequate to fully charge the TC battery when the truck engine is running. Here is how I addressed both issues.
Boatycall
Explorer
May 19, 2014
Well, first, welcome.

We need to know what kind of truck you have. Guessing from your screen name, a Chevy. FYI, if you could, fill out your Signature in "preferences". But regardless, the 12v accessory pin is NOT supposed to be energized when the truck is off. There may be something mis-wired in your 7-pin.

And yes, at 11v, you either have one very low on water, or you need a new battery. I (like many others here) would recommend 2 golf cart batteries rather than RV Deep Cycle.
lanerd
Explorer II
May 19, 2014
My guess is that your TCs battery is either discharged or very low on power and is not being charged. I assume you have a multimeter and can measure the voltage at the terminals. If anything less than 12.4 volts....put it on a battery charger.

You need to get it up to 12.6 volts "after" it has been charged and disconnected from EVERYTHING for an hour or so. Anything less than say 12.4 volts is indicating that the battery isn't holding a charge (for one reason or another) and you need to replace it. If you do replace it, make sure the new one is a Deep Cycle and is measured in "amp hours" and not "cold cranking amps". Big difference.

As for the solar panels, 11 volts is not near enough to charge the battery...you have a problem there, or maybe just not enough sun?

I would also guess that you don't have a built-in converter that has a multistage battery charger as part of it and the only charging capability is the solar panel...correct? If no converter and your solar panels aren't putting out sufficient power, then you will need to recharge the battery almost daily while camping...so for this you'll need 120v hook up or a generator and the charger, of course.

Pulling the fuse would be an easy way to disconnect the truck batteries from the camper's battery. You might want to think about putting in a switch that will disconnect the fuse without having to pull it.

Good luck

Ron

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12 volt system - Okanagan UDB

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