Forum Discussion

Duramaximos's avatar
Duramaximos
Explorer
May 19, 2014

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
  • cewillis's avatar
    cewillis
    Explorer
    May 22, 2014
    tony lee wrote:

    Perhaps, but I get the impression that US RVers are still very much in the conventional flooded lead acid camp rather than AGM, so it might just confuse the OP to give your results.

    I don't think that's true at all.
  • tony_lee's avatar
    tony_lee
    Explorer
    May 22, 2014
    cewillis wrote:
    Just as a reference point, ~6 hours after a float charge, my AGM camper batteries show 13.1 v. (same Sperry multi-meter)


    Perhaps, but I get the impression that US RVers are still very much in the conventional flooded lead acid camp rather than AGM, so it might just confuse the OP to give your results.
  • cewillis's avatar
    cewillis
    Explorer
    May 21, 2014
    Just as a reference point, ~6 hours after a float charge, my AGM camper batteries show 13.1 v. (same Sperry multi-meter)
  • rskeans's avatar
    rskeans
    Explorer
    May 21, 2014
    I also have an Okanagan but on a 2014 RAM. I had the camper mounted on the truck, but disconnected the camper batteries with the knife switch. I went into the storage compartment and noticed that the compartment light was light. ??? Did some trouble shooting and found that the power was coming from the truck batteries. Note that the RAM was off.

    It turn out that RAM does not have an isolation relay from the truck batteries and the 7-pin camper connector. The truck battery only goes through a fuse in the truck fuse box.

    I brought this up on a RAM forum and about half of the respondents were aware of this problem. Most disconnect the 7-pin when they dry camp because of this problem.

    Now, someone in that same forum stated that Chevy trucks are also directly wired just like the RAM. If so, that could be the problem.
  • Duramaximos's avatar
    Duramaximos
    Explorer
    May 21, 2014
    AnEv942 wrote:
    I assume the controller display alternates between voltage and current, voltage showing status of battery, current being the amps sent to battery. What is max 'current' you've seen displayed? (with battery hooked up).

    Meter-check against the panel meter..when camper plugged into truck-solar meter showing 13.1 or what ever, your multi meter should read close to the same at truck battery.

    At 14+, the batteries on charger? My assumption. So camper battery took charge? Has it stabilized, holding charge since last night?


    Yes you're correct the display alternates between voltage and current. I believe the max current I've seen is slightly over 1, perhaps it was 1.3, but most of the time it is around 0.5.

    The TC is in storage at the moment so I'll complete the tests you asked for later this week.

    I do have the battery at home and it has been sitting for over a day now since it was last connected to the TC and solar panel. The voltage is sitting at 13.95. I also switched it to the 200 setting and it reads 13.9. I also remeasured the spare battery and it is reading 13.8 today. Neither of these measurements were taken while connected (or recently connected) to a charging device.

    I'll be buying or borrowing another meter later this week and will report back.

    Thanks.
  • AnEv942's avatar
    AnEv942
    Nomad
    May 20, 2014
    I assume the controller display alternates between voltage and current, voltage showing status of battery, current being the amps sent to battery. What is max 'current' you've seen displayed? (with battery hooked up).

    Meter-check against the panel meter..when camper plugged into truck-solar meter showing 13.1 or what ever, your multi meter should read close to the same at truck battery.

    At 14+, the batteries on charger? My assumption. So camper battery took charge? Has it stabilized, holding charge since last night?
  • tony_lee's avatar
    tony_lee
    Explorer
    May 20, 2014
    Before tossing the multimeter - could be just the battery is flat.

    Also could try it on the 200V scale to see if the reading is the same
  • Duramaximos's avatar
    Duramaximos
    Explorer
    May 20, 2014
    tony lee wrote:
    Use that multimeter (with the leads reversed - black to common) to check any starter battery with the engine not been running for an hour or so. Should read between 12V and 12.8V depending. Too much higher and the multimeter is suspect.


    haha, told you I am a newbie!
    I reversed the leads and the reading is still the same. Two batteries measured between 14.1 and 14.2 volts while disconnected.

    Guess I'll be replacing my multimeter tomorrow!
  • tony_lee's avatar
    tony_lee
    Explorer
    May 20, 2014
    Yes, the system proposed by cewillis is one of the simplest, cheapest and most effective ways to get some decent charge into the camper battery from the engine alternator. The shorter and thicker the connecting leads, the better it will work.
    If it could be combined with as much solar as can be fitted onto the roof, then depending on the charging characteristics of the alternator control system (and not all are equal when it comes to charging remote batteries) the engine will provide a decent contribution towards charging the camper batteries while driving and the solar can finish it off.

    Use that multimeter (with the leads reversed - black to common) to check any starter battery with the engine not been running for an hour or so. Should read between 12V and 12.8V depending. Too much higher and the multimeter is suspect.

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