Re: Charging from tow vehicle

On Sat, 8 Mar 2025 19:38:39 -0000 (UTC),
  Ted Heise <theise@panix.com> wrote:

 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.

A couple of additional thoughts I meant to work in.

First, I expect the fridge was at its max demand when I tested
yesterday, because I'd just started it up.  Seems the draw would
be less (at least the duty cycle would be lessened) once the
inside has reached temp.

Second, it seems possible that once the Acadia's battery has been
fully charged the alternator output might drop and the trickle
charge going out via the 7-pin to the Lance would also drop.  I
figure I can watch this next time we are actually towing.

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