Re: Charging from tow vehicle

On 3/7/2025 10:55 AM, Ted Heise wrote:

On Thu, 6 Mar 2025 17:56:09 -0600,
   sticks <wolverine01@charter.net> wrote:

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

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

 

   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.

 I think that's probably correct.  Here is the (typical) exterior
wiring diagram from the manual...
 https://panix.com/~theise/wp-content/uploads/2025/03/Lance-1475-ext-wiring-traced.pdf
 This shows that the 7-pin does connect to the battery, and seems
consistent with the trailer manual statement that "Normally the
battery will be kept charged by either the tow vehicle charging
system while on the road or by the AC/DC power convertor when
plugged into AC service."  It looks like the TV is wired directly
to the battery and not by way of the PD4000 load center (though
it's also wired into the load center).
  From some sites I've looked at while trying to figure this all out
(can't remember where) I've gotten the sense that the Acadia would
be trickle charging the trailer battery.  And of course the car's
system is designed for lead acid chemistry, so isn't going to be
very (or at all) effecive for charging the trailer's lithium
battery.  I also have the sense that the fridge must draw more
than the Acadia supplies and be drawing the difference from the
trailer battery when towing.

Your pic show about the same thing I found out today.  First, I got two pics from the manual and the first from page 50 does state the power prong on the 7 prong plug goes to the battery and will provide charge.
<https://postimg.cc/gallery/r4xVRjj>
The second pic is similar to your showing the PD4000 as well as the 7 prong.  It has a smallest size of 8 gauge right at the generator and has a capability of 35 amps, though it has a 30 amp inline mini breaker. This would be a nice setting for charging the Lithium and probably close to what you'd get if you did a DC to DC generator at either 20 or 30 amp.
I would agree this setup is not really taking into consideration having a lithium battery, though I don't think ti hurts anything if you leave it as is and go ahead and install a DC to DC converter.  It is just a trickle going to that.

The Lance manual also says, "The 30 amp main circuit breaker
located on the chassis in the car connector junction box will not
allow power into the trailer or the battery(s) to be charged when
an overload or short circuit occurs."  That said, I'm not sure
this junction box warrants further investigation so long as the
trailer is getting power.  Stil need to double confirm the trailer
is in fact getting power from the Acadia, and will try to get that
done tomorrow morning.
 

  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.

 Yes, correct, there are AC outlets in the Lance.  Looks like the
power goes from the shore line to the outlets by way of the load
center...
 https://panix.com/~theise/wp-content/uploads/2025/02/Lance-schematic.jpg

Yep.  You plug in your shore cord, you will get power at the AC outlets. Since you have no inverter, these should be dead unless you plug in the shore line.

 

      ...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.

 Pretty sure there is no inverter in the trailer (though it seems
there must be one in the Acadia to run its low power AC outlet).

Yes, any AC outlets in the Acadia have to be powered by an inverter. They're getting quite big these days.  I think yours is 150 watt max.  I remember years ago I needed one on my work truck and spent a good penny on a 100 Watt.  I could run my laptop at work and other things.  I thought I was so cool  Ha!

 

  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?

 Yes, there is a brake controller in the Acadia, installed by the
RV dealer I got the Lance from.

Great.  You got brakes!

 

  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.

 So the diagram I posted shows the power does go from the Acadia to
the Lance battery.  Is that a problem?  I don't think there's any
other kind of control box, unless it's in the junction box under
the Lance tongue (or maybe in the Acadia's tow system).

You could ask the dealer if this can be left alone if you add a DC to DC converter, or even if they think it will harm the alternator on the Acadia, but I don't think it would matter and could just be left alone.

 

  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?

 Yes, the interior lights go on with no battery in place (or with
it and disconnected), I think the wiring schematic shows it goes
into the load canter.
 

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!

 Thanks!  Just sporadic supraventricular arrhythmias, not a fib.
Pretty benign according to the cardiologist.

Good to know.  Keep the rubber down!
--
Better Days Ahead!
Darwinism Is Junk Science!!