Re: battery change questions

On Sat, 3 Aug 2024 15:38:30 -0500,
  George Anthony <ganthony@gmail.org> wrote:

 On 8/3/2024 1:00 PM, bfh wrote:

Ted Heise wrote:

On Fri, 2 Aug 2024 23:13:42 -0400,
   bfh <redydog@rye.net> wrote:

  Ted Heise wrote:

But how did you charge the trailer battery?

>
  It charged through the 7-pin when driving, and with the
  built-in charger when we had shore power. I don't remember
  having any battery problems when flatspotting, but we rarely
  stayed in one place longer than 2 days/nights. Plus, we weren't
  spoiled back then, and all we used when parked were 1 - maybe 2
  - lights and the water pump.

>
Okay, charging from the 7-pin is what I'd expect, but I
haven't seen any evidence of that happening since I put in
the new LiFEPO4 battery.  Admittedly, it's just been one trip
of ~5 days.
>
I do wonder if the battery has to reach some lower SOC than
I've seen (85%?) for charging from the 7-pin to kick in. 
Operation of the Dometic battery monitor is still largely a
mystery to me...
>
https://www.amazon.com/Go-Power-GP-BMK-25-Battery-Monitor/dp/B09NRXD9G8
>
Is it possible the 7-pin will actually charge the battery if
it gets to a lower SOC?  If yes, do the GP-BMK-25 settings
make a difference in this level?  I can't tell from the
"manual" and mre broadly havn't been able to get a good
unserstanding of how it works.

 
 I really don't think it will charge from the 7-pin connection
 if the battery is low. At least not with the standard size wire
 you now have. By the way, I may have missed it but did you ever
 verify if you have voltage coming through the 7-pin connection
 at the positive battery cable on the trailer battery?

Yes, I've checked the 1 and 4 pins on the 7-pin receptacle with a
multimeter, and there is 12 V there--even when the car is shut
off.  I'm also able to run 12 V equipment (e.g., tongue jack,
lights, exhaust fans) when the trailer (without any battery) is
connected to the 7-pin on the tow vehicle.

The thing that doesn't make sense to me is that when the battery
and 7-pin are both connected, the battery still reports it's
discharging.  I could get that it doesn't charge much, but to be
discharging just seems unexpected--like something in the trailer
(e.g., the PD4000 power control enter) is not supplying anything
to the battery.  FWIW, it does charge when the trailer is hooked
to shore power.

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