Mercedes E Klasse battery malfunction

I understand you are experiencing issues with your Mercedes E Klasse. A similar issue occurred with my own vehicle, which shares the same model. The symptoms you describe, including the error message, stored error codes, and weak battery performance, strongly suggest a problem with the auxiliary battery. Have you checked the connections to the auxiliary battery for corrosion or looseness?

Good shout on the connections, I'll double check those. When you had the similar issue, did you also experience any other electrical weirdness, like the interior lights flickering or the infotainment system acting up?

Affirmative, I did observe some ancillary electrical anomalies, such as intermittent operation of the interior illumination and disruptions to the infotainment interface. Given your description of parallel symptoms, it is my considered opinion that the most judicious course of action would be to seek diagnostics from a qualified automotive technician. While component replacement may ultimately be indicated, professional assessment will provide definitive confirmation.

Thanks for confirming that, really appreciate it. Ended up just swapping out the auxiliary battery, and that seems to have sorted it. Voltage is back to normal, no more error messages, and the electrical gremlins are gone. Seems like it was just a dead battery after all.