From: wolverine01@charter.net   
      
   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.   
      
   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.  Mine was wired with 12 gauge wire, and I did install a 12 gauge   
   and a fused link that went from the umbilical directly to the battery on   
   my Toad.  This, however is a regular automotive battery and not a   
   Lithium battery.  This would NOT work for charging a lithium as it needs   
   a converter/charger before the lithium, and even if I did have one, the   
   trailer 7 prong is probably only going to be able to provide between   
   5-10/12 amps and that would not be enough to fully charge a lithium   
   battery.   I think you need at least 20 amps to ever get a lithium   
   charged.  (This is where having a bigger alternator could be useful, as   
   you could get a 40 amp or bigger charger greatly speeding up charging.)   
   Therefore, a DC-DC charger is the next logical option (setting aside a   
   perfect solar charging install).   
      
   The next question is what is available on the trailer.  Ted, for example   
   can plug into shore power, and even use his 7 prong, or so he thinks.   
   So what exactly do you have on the trailer that deals with recharging   
   the house batteries if anything?  Does it already have a charger that   
   would be capable if you could only get it enough power?  When you're on   
   shore power, does it also charge up the lithium batteries?   
      
   On mine, for example, the house batteries will charge off the alternator   
   when running, and will get charged off the shore power when plugged in.   
   They also get charged by my solar panel on the roof.  I believe if I am   
   on shore power, there is something in the controller that switches off   
   the solar, but I'm not positive on that.   
      
   So, I think it is a certainty you cannot get enough power simply off the   
   7 prong to do much of anything.  So a DC-DC charger is a perhaps, but a   
   6 gauge or bigger line for power to the trailer is a must.  Now, you   
   have to figure out what you already have on the trailer that you could   
   use, if anything, and what you will need to get.  Next step is becoming   
   certain of what is on the trailer now.  Would also be a good time to get   
   a better understanding of what that solar plug it has installed actually   
   does.  For example, does it just give a route for power from a solar   
   source and charger/controller to the batteries, or does it actually have   
   any of the hardware in the path?  On mine for example, I have a similar   
   solar plug that I can add additional panels to which I believe are then   
   used by the internal RV controller/charger.   
      
   please remember this is all new to me too, and I'm trying to work it out   
   as we go too, so I've probably made some false assumptions.  That said,   
   I think if we go step by methodical step, we can figure out how to   
   properly deal with all this in an informed manner.   
      
      
      
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   Better Days Ahead!   
   Darwinism Is Junk Science!!   
      
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