From: wolverine01@charter.net   
      
   On 3/5/2025 2:03 PM, Ted Heise wrote:   
   > On Wed, 5 Mar 2025 09:05:19 -0600,   
   >    sticks  wrote:   
   >>   On 3/5/2025 7:41 AM, Ted Heise wrote:   
   >>   
   >>> So I looked at the manual for the fridge, and it clearly   
   >>> states it only runs on 12 V if the trailer is connected to a   
   >>> running tow vehicle.  I guess the next step in better   
   >>> understanding the issue would be to hook up the trailer and   
   >>> check the battery status while the fridge is running on 12 V.   
   >>   
   >>>>    Regardless, it seems pretty clear my Acadia tow vehicle is   
   >>>>    not producing enough juice to help.   
   >>>   
   >>> If I want to look into getting a DC-DC charger and cable to   
   >>> back of my Acadia installed, where would I start--is that a   
   >>> GMC dealer thing, or an RV shop?  Other?   
   >>   
   >>   OK, this is a good place for getting started on what I was   
   >>   suggesting we do to get some consensus on this charging of   
   >>   trailer batteries universal problem for us RVers.   
   >>   
   >>   The first place to start would be the 7 prong plug in, on the   
   >>   tow vehicle, and the vehicle being towed.  I am going to take   
   >>   it for granted most of us would be using a 7 prong plug.  Any   
   >>   differences are minimal and easily solved.   
   >   
   > Agree this is a good place to start, and you actually anticipated   
   > my next step.  I've been puzzling over in my head on the lack of   
   > charging while towing.  The Acadia does have a factory installed   
   > 7-pin connector right next to the receiver.   
      
   >>   So let's start on the tow vehicle.  It might surprise some of   
   >>   us that our plugs don't even have power in them as delivered   
   >>   from the factory. I have an F-150 and was quite surprised   
   >>   myself that I had to install an additional fuse to get my line   
   >>   hot.  It was wired, but not fused and inactive.  With today's   
   >>   CANBUS systems, it can be difficult testing this, and you   
   >>   really have to use a 12 volt test light and not a volt meter.   
   >   
   > My thinking was to take a reading from the LiIon battery app with   
   > the battery connected to the trailer and then with the fridge   
   > started (I think it may run off the batt for a minute or two).   
   > Then I would connect the 7-pin to the running TV and repeat these   
   > readings.  Does that seem like a reasonable approach?   
      
   In truth, I think it is pointless in your case.  I think we already have   
   agreed now you simply cannot get enough power to charge your lithium   
   batteries from the 7 prong.  I would, however,  like to know if there is   
   power coming in, and going out to the trailer.  If there is a power wire   
   hooked up on the 7 prong on the trailer, where exactly does that power   
   go?  Obviously the trailer lights you can easily figure out, and they   
   don't use power from the trailer battery.  They draw directly from the   
   towing vehicle.  Usually the power tab is for trailer brakes, or an   
   accessory of some sort or another.  Were you under the impression it   
   somehow went to your battery?  Obviously it can't go directly there   
   since it would be incapable of charging lithium batteries, so does it go   
   to the controller you speak of later?  You need to find out exactly   
   where that power goes, and here's why.   
      
   I sense there is a possibility you could use the controller to charge   
   your batteries just as it does on shore power.  The question would be   
   does it have the ability to invert DC to AC, which would be what you get   
   when you plug into shore power.  However, if your 7 prong power tab is   
   going to this controller, perhaps you can use this.  I'll try and read   
   up on it tomorrow a little more.  But, though my View is a single unit,   
   this is exactly what it does somehow.  On shore power it charges up the   
   house batteries nicely.  Once I turn on the engine, it still charges up   
   the house batts, but it uses the alternator and now DC current.   
      
   Now you don't need to use this and can easily just install a DC to DC   
   generator as they can properly charge lithium batteries.  To me it seems   
   like 20 amp is the sweet spot when trying to use a 12 volt system with a   
   single battery and standard alternator to do this.  Larger alternator   
   and double battery obviously gives more options.  You do have to get the   
   6 gauge or larger wire back to the trailer somehow, for either scenario.   
     You need to find out where that power lead on the trailer side of the   
   7 prong actually goes.   
      
   FWIW, this wiring in your case should not be all that complicated as you   
   could simply go in the engine compartment and go right out the bottom,   
   encase it in some hard shielding, and zip tie it right along the frame   
   rails.  I did small portions of this on my Bronco, and that is going to   
   be doing some off road stuff.  (though I've heard somewhere you like to   
   bounce over railroad crossings 8-)  You just have to figure out what   
   type of plug you want and where to mount it.  If you would rather not   
   attempt this, this is exactly the type of work RV places do.  I'm rather   
   fortunate in that I have a family owned fantastic Winnebago dealership   
   who can do my work.  I would completely avoid Camping world, RV center,   
   and any other of those large chain stores.  They suck.  Small   
   independently owned auto repair places can also do this type of work,   
   and you can find some good ones.   
      
      
   > I need a block of time to get out to the storage unit for this, so   
   > in the meantime I figured I'd take some measurements at the 7-pin.   
   > First I connected clips from my multimeter with the TV off.   
   > Surprisingly, I got some sparking, may have been from touching   
   > across pins.  But once I had a good connection I got no voltage.   
   >   
   > Now this could be from the line not being hot (e.g., because of a   
   > fuse needed), or because a multimeter won't work.  But I vaguely   
   > recall having gotten a 12-13 V reading from the pins some time in   
   > the past.  So maybe the sparking blew the fuse.  I'm trying to run   
   > down where that would be and will let you know what I find.   
      
   I believe your Acadia is a 2022?  It almost certainly will be utilizing   
   lots of the CANBUS technology.  What this means for the power plug on   
   your 7 prong is that it won't send any voltage unless it senses a load.   
   That's why multi-meters usually will not work to see if they are hot.  I   
   had to figure this out the hard way myself and once I bought a cheap DC   
   test light it provides a load to the system and lights up.  You can try   
   a meter, but the only way to know for sure if you're getting nothing is   
   to use a test light.  I have not had my TOAD pulled behind my view yet,   
   and the only way I know it should work is because the proper plug did   
   light up with a test light.  Got nothing with a multi-meter.   
      
   >   
      
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