auxiliary battery failure

[MercedesFan2022]

Greetings to everyone,

My vehicle was in the shop for two months, and upon its return, I saw a "auxiliary battery malfunction" notification on the dashboard, leading me to consider that it may need charging or replacement. I assessed the battery's condition, and the voltmeter indicated a satisfactory charge of 12.6V. Additionally, I connected it to the charger, which displayed a Full Charge status. I connect the automobile to a charger, and it has provided

C073300, "Retrieve fault memory from control module."N10 (SAM Control Module) B1E211B The buffer battery is defective. The resistance limit value has been surpassed.

I have wire brushed the connections, nevertheless the same issue persists.

Is the voltage measurement an inadequate indication of the battery's condition, or should I assess other components inside the vehicle?

Thank you very much.

[William_Brown2000]

Which automobile is it? Is it not possible for it to be the 2008 CLC?

I changed the 12 Ah auxiliary battery in my W222 twice due to the same problem code. The old battery exhibited optimal voltage under no load; nevertheless, when attaching a 21 W bulb, the voltage decreased by several volts (precise values not recalled).

[MercedesFan2022]

2015 E-Class Coupe.

[jane_doe2023]

The open circuit voltage does not inherently signify a battery's quality. It is necessary to do a load test.

[MercedesFan2022]

I will accomplish that! Thank you very much

[almamater78]

Examine your primary 12v battery as well. When my device reached eight years of age, it failed to maintain the auxiliary battery's charge.