Re: Charging from tow vehicle

Okay, I'm a dumbass.  I made up a table of the various cases I
wanted to test, but when I got back from a couple of hours at the
storage place and started writing up a summary I realized I had
filled in the most critical combination with info that should have
gone in a different row.  So I had to go back and test that last
case.

Bottom line is the Acadia will in fact charge the LI battery
installed on the Lance via the 7-pin connection, but with the
fridge running the battery discharges.  See inline for more.



On Fri, 7 Mar 2025 11:48:30 -0600,
  sticks <wolverine01@charter.net> wrote:

 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:

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).

I've confirmed that the Lance's 12 V system is powered when
connected only to the running Acadia via the 7-pin cord (i.e.,
without the LI battery connected).  As expected, the 120 V system
in the Lance does not have power in this case.

I think that [PD 4000's limitation] is 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."

 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.

I looked at quite a variety of things, but the gist of it is that
voltage at the LI battery when connected to the running Acadia
mirrors that on the Acadia's dash gauge: in the vicinity of 13.4
to 14.0 V.  The LI battery app shows that it's getting about 2 A
from the Acadia.  If my rough calculations are correct, 6 hours of
towing would add back about 12 Ah, so the charging at this rate is
not going to be fast.

FWIW, the LI battery app showed 0.6 hours to full charge at the 2
A rate when it was 98/99% full.
 

  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.

Correct, no juice at the 110 V outlets when on the Acadia and/or
the LI battery.

Interestingly, I noticed an old cigarette lighter plug-in on an
interior wall receptacle along with a 5 V USB jack.  I'm guessing
that would provide 12 V.

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.

I think this is right.  The low power over the 7-pin is pretty
unlikely to ever get the LI battery up to full, unless it's very
close before starting a day of towing.

I also tested the system with the fridge running.  With only the
LI battery connected, its app showed the fridge was drawing about
17 amps and that it would be discharged in under 6 hours.  With
the running Acadia also connected, the LI battery app showed a bit
over 7 A draw, with somewhat over 14 hours of runtime left.

From this, I take that the fridge draws so much that it robs from
the LI battery as well as from the Acadia.  My impression is that
if the LI battery is relatively full at the start of a towing day
I should just disconnect it while towing so it doesn't get drawn
down and it's SOC is preserved.  The fridge should run okay on
only the jiuce from the Acadia via the 7-pin.

on the other hand, if the LI is low on charge when I start a day
of towing, I could consider leaving it connected and running the
fridge on propane.

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.

So to recap, I'm now thinking the Acadia can charge the LI
battery, albeit on the slow side.

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!

Thanks!  The temps here are approaching 50 F and the wind is light
(for here), so I'm gonna head out on the bike shortly.  Will do my
best to keep the rubber down!

--
Ted Heise      <theise@panix.com>       West Lafayette, IN, USA