The BMV-712 by it's default configuration will "falsely synchronize to 100% SOC" when combined with solar panels unless you actually read the manual and set things up accordingly.
This also contributes to the previously incorrect data I once provided on "how quickly the solar can recharge after running a 12 volt compressor refrigerator overnight".
The settings that need to be carefully inspected and set up are in bold as follows, the rest are the settings that I used that do not affect the interaction with Solar Panels.
Battery Capacity - I know, everyone had to set that up initially
Charged Voltage - this is automatically set based on the detected voltage IE 12 Volt is set to 13.2 Volts - this is NOT correct for use with a solar charging input. It needs to be set to 14.2 Volts
Discharge Floor - not that important because you can base the remaining energy on the display of the BMV-712 - ** appears to be used for Relay control more than anything else
Tail Current - I believe the default is set at 2% but based on the manual for the BMV-712 it should be set to 4%
Charged Detection Time - Default of 3 Minutes is fine
Peukert exponent - set to 1.10 based on Victron's app and the Harris Battery Info, mine was set to 1.25
Charge Efficiency Factor - was set to 95% but from what I was able to find on the info highway, AGM are about 80% ** Harris Battery confirmed that 80% is the correct value to use for their batteries
Current threshold - default of .10 Amps is fine
Time to go averaging period - default of 3 minutes is fine
Battery starts synchronized - default it is on, I turned mine off. It is my understanding that if your master switch turns the power off to the shunt, it will reset to 100% on power up regardless of the actual state of charge.
So, here is where I got into my "situation". Recently on 3 nights of boondocking, I woke up on day 1 having used roughly 55 amps of my available with a SoC of 81%. I turned on the invertor and made my coffee as usual, taking about 6 amps over the course of the 5 minutes to brew. Went hiking, came back a few hours later to find SoC at 100%, all is great!
Day 2, I wake up and once again I had used roughly 55 amps and had a SoC of around 80% remaining. Went to make coffee and it was a no go, there wasn't sufficient voltage available to operate the invertor under the high demand (draws about 55 amps) while brewing. So, I connected my generator and made my coffee.
In roughly an hour, I had "fully charged the batteries (BTW I am using a PD9260C installed within 12" of the battery junction block) but as I watched I could see that even though the BMV-712 showed 100%, that I was still pushing 40 amps into the batteries. This was obviously letting me know that "100% wasn't really 100%" based on the rate of charge still going on.
One would think that if you had something monitoring the amps used that once those amps were replaced that this would initiate the synchronization to 100%. However, that is not how the BMV-712 actually works.
Synchronization occurs as follows:
Example: by default if the Voltage is greater than 13.2 and the amperage flowing is less than 4.48 amps for 3 minutes, the BMV-712 automatically sets the SoC to 100%.
In order to overcome this, you need to set the Charged voltage to .2 volts less than the Absorption voltage (14.2 with the OEM installed Harris AGM's). This alone should correct the issue, but I also set the Tail current to 4% based on the BMV-712 manual. There was no need that I could think of to change the time period that these 2 conditions needed to be met.
So now in order for SoC to be synchronized to 100%, I need to see greater than 14.2 volts with less than 8.96 amps flowing for 3 minutes.
Disclaimer... I am still working on a couple of these settings and the Tail current being set at 4% of the amp capacity of the batteries may be too high (even though that is what Victron recommends). This is a work in progress and I will update things as needed.
Edited adding information noted with asterisk
2020 400 BDL
2021 F-250 Tremor with PSD