E350 Battery Alert

[tomatoeincluding]

Greetings everyone,

I purchased a 2006 E350 some weeks ago. I have mostly been driving it daily. It has been rather pleasant. While traveling to work today, I saw a faint picture of a battery accompanied by the words "Visit workshop!" on the speedometer display. The lighting of the gauge cluster screen has malfunctioned, rendering it visible only under optimal sunlight conditions. I resolved to measure both batteries using a meter. The primary battery measured 13.1 volts while the vehicle was off and 14.7 volts when the vehicle was operational. It is dated April 2022. The auxiliary battery measured 12.5 volts while the vehicle was off and 12.5 volts when the vehicle was operating. It is dated February 2021. My trunk had a significant leak originating from the passenger side taillight, which has subsequently been rectified. I suspect the BCM. Furthermore, the inside lights that typically activate upon opening the door are nonfunctional, but the radio, seats, and heating/air conditioning systems operate normally. My sunroof is inoperative. Is it typical for my auxiliary battery to remain at 12.5 volts regardless of whether the vehicle is operational? Does this seem to be a BCM issue? I value any perspective. I transitioned from a W126 to this, so I feel rather overwhelmed.

Thank you.

[mindscoop]

Indeed, the auxiliary battery is segregated from my circuit by a switch, which activates just after the ignition if the BCM/ECU detects a low voltage in the auxiliary battery. While there may be a relay malfunction, it is necessary to get the diagnostic codes.

Inspect the BCM wire, since it is susceptible to corrosion.

The voltage regulator may be nearing the end of its lifespan, and an occasional voltage decrease while charging might have triggered the alert.