My W211 has been getting the above message last winter, and it goes away after driving 2-3 miles. Recently I had the battery tested at 2 Auto parts stores and both of them said that the battery is good, as is alternator and the battery needs charged ( mind you since my retirement I just drive 5-7 miles each way). Is it possible I just drive very little and that may be causing it ? I have a charger and was planning to leave it charging over the weekend. Do I need to disconnect the terminals on main battery and do I need to disconnect the auxiliary battery ? Thanks in advance for any advice.

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