Re: Battery charging/discharging

 On 6/13/25 8:28 PM, sticks wrote:

On 6/13/2025 7:20 AM, Ted Heise wrote:

On Thu, 12 Jun 2025 19:48:51 -0500,
   sticks <wolverine01@charter.net> wrote:

  On 6/12/2025 12:44 PM, Ted Heise wrote:

 

FWIW, here are the details from each of the three test
cases...
>
7-pin        Power     Current   Voltage
Connected    -220.1 W  -16.7 A   13.2 V
Dis-connect  -242.2 W  -18.5 A   13.1 V
Connected    -215.7 W  -16.4 A   13.1 V
>
And this was all with the battery SOC being about 98%.

>
  I can't recall from the earlier discussions, but where does the
  hot prong on the 7-pin on the trailer go to?  Does it have a
  wire going to the battery?

 
I think you may have asked this question before, but am pretty
sure I would not have answered it because I'm not sure how to
tell.  Is the idea to see what role the trailer's power center may
play?

>
First off, I don't see how the the towing vehicle would lower the
battery on the trailer, but I'm not positive on this. The power to the
7-prong comes from the battery and when running the alternator will keep
the voltage over 12 volt.  Usually something like 14.4 volts.  This is
one of the reasons DC to DC chargers are used to protect the alternator,
but IIRC you have a heavy duty alternator.  I can see when you turn off
the tow vehicle and if you don't have it isolated, the Acadia could be
backcharging from the lithiums.  If the Acadia is running, it might not
give enough power to charge, but I can't see how it would pull power
from the trailer.
>
That said, I'm not sure what the power center you mention is, but I
would want to know where the power wire from the 7-prong on the trailer
goes.  Your signal and brake lights do not use power from the trailer
batteries.  They use the towing vehicles power.  Often, the power prong
is used for trailer braking I believe.
>
On my TOAD setup on our Bronco, I installed a wire from the 7-prong and
put a fuse in the route, and took it directly to the battery.  It kept
the TOAD battery fully charged with an electric Patriot Brake that I use.
>
If it were me, I would follow the wire on the trailers umbilical from
the power prong and find out where it goes to start with.  Now I don't
have lithium batteries, but I recall when we were discussing this before
there is a little difficulty getting them to start charging, and we
agreed on 3/7 you could not get enough power from your tow vehicle to
charge them.  We also kind of agreed there is a wire going to the
battery per manufacturer literature.
>
Message-ID: <vqfbhe$3ict3$1@dont-email.me>
>
This is one of the reasons people install those DC to DC converters.  I
think they will charge at a steady 20 amps with a good size wire, and
higher if you go down to say a gauge 4 wire.
>
--
Darwinism Is Junk Science!!

 
 I think you are on the right track. Lithium batteries wont charge directly
  from a cars alternator. Trying to do so might damage both car and trailer
  batteries. Best to check with trailers dealer to see if trailer is set up
  properly.