Re: Charging from tow vehicle

On 3/6/2025 7:54 AM, Ted Heise wrote:

On Wed, 5 Mar 2025 19:55:25 -0600,
   sticks <wolverine01@charter.net> wrote:

  On 3/5/2025 2:03 PM, Ted Heise wrote:

 

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.

 Okay, here are some aditional points of information.
 I'm positive there is power coming out of the 7-pin connector,
because I've frequently operated the powered lift jack without any
battery connected (i.e., only the 7-pin connected to the trailer).
 Pretty sure there is power going into the trailer too, because my
memory (though not certain) is that the interior lights and other
12 V things work in the same circumstance (i.e., no battery
connected, just the running TV).

It looks like the PD 4000 power controller you have only does one thing that I can tell, that being to convert AC power into DC power.  It operates when it is plugged into shore power and charges the batteries, but will also provide power for the DC power outlets without the need for the battery.  So you can rule out using this controller for charging from the DC supplied power from the 7 prong plug.
So you do have some AC outlets in the unit I believe, and these most likely only work when the shore line cord is plugged in.  There might be a disconnect switch somewhere, but it probably just has a bank, or something like a electrical box that ties in all the AC outlets to the shoreline somehow.  To get AC power without being plugged in, you would need an additional inverter that would change the DC battery power into AC for use at those outlets.  So far, you have not said you have such an inverter.
I think you're ability to use the lift jacks off the 7 prong is interesting.  I think it is probably wired mainly for trailer brakes, although it looks like the dry weight of your unit is around 3,000 lbs and 4,000 is the legal requirement for trailer brakes.  Do you have a brake controller in the Acadia and use trailer brakes on your Lance?
How else it could be wired into the Lance's volt system is an interesting question. You say you think you also get lights.  Sounds like there must be some other kind of control box then if this is true, and I would certainly follow the power lead off the 7 prong to find out where it goes.  Mainly, because it should NOT be going directly to the battery since it is a Lithium.  You simply cannot charge a Lithium battery properly from the alternator of a modern vehicle on it's own. It would never charge the Lithium, and it could harm the alternator. That capability requires the addition of the DC to DC generator.
You say you get these lights "without any battery connected."  I'm assuming you mean you either have a disconnect switch, or you have the battery cable actually disconnected.  You see what I'm getting at?  If the interior DC circuits have no access to the battery, how is it they are getting power from the 7 prong.  Where does it get hooked into the system?

As I lay awake in bed last turning this over and over in my mind,
I seemed to recall the Acadia had a 110 V outlet in the second row
of seats.  Indeed there is when I checked it this morning.  Rated
at 150 W max, it seems I could use this with my NOCO GENIUS 5
charger (max 75 W draw) to charge the trailer battery in a pinch.
Might could even use it to run the coffee grinder.  ;)

It looks like this unit is more for non-lithium batteries, but it does say it can charge them.  I'm not sure, though.  Doesn't seem to have enough power capability to do much of anything.

Gotta run to see the cardiologist now, but will come back to this
later today.

Hope you got some good reports!
--
Better Days Ahead!
Darwinism Is Junk Science!!