When your Mercedes says your aux battery is malfunctioning, you need to replace it. This is on a 2010 R350, but it applies to many Mercedes vehicles.
Don’t go to Mercedes, they’ll charge you $$$$$$
Get one of these batteries: amzn.to/3YzYjMc
And a bunch of 10mm sockets: amzn.to/3v44daY
And you should be good to go!
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