I have a 2011 550 cabriolet. It has only 25k on it yet it has gone through two batteries already. Why?
Only thing you may check,is make sure all light,s and power is off in car,then,being it is a mercede,s,may want to check your ignition switch it self,it is the source of power.
If you live in a hot climate this car also effect the life of your battery.
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