My 2001 S430 w/ 9000 miles (yes 9000) has been experiencing dead batterys within the last year. History- Obviously, I don't drive it very often. But the orginal battery lasted 5 years ! I had a new one istalled last year and within 6 months it died. Had roadside out 3 times this nasty winter and even bought a trickle charger ( cigarate ligther type - use same type on another car and works fine, also swapped chargers - no luck) Anyway, since my battery was less than 2 years old, they gave me a new one last week. Weather has been mild last week and I put the charger on. Went out yesterday for a spin and DEAD again. What the "hotel" is going on? This car is still brand new- even still smells new!! Why after all these years of the same usage pattern am I having problems? HELP !!!

 

Need to determine quiescent drain on battery.
Maybe something is remaining on whebn you remocve the key. Everything SHOULD shut down after 10 mins or so even if Interior Light etc is left on.
Guess that the computer is not shutting down for some reason.
I wonder whether your "trickle" charger might be keeping the computer awake. Mmm. Not sure.
Of course the "NEW" battery may have been defective.
Where did your replacement battery come from? Is it the correct rating? Genuine MB part or some unknown aftermarket replacement?
Stuart

 

Battery was new from roadside service tech. It runs down without the charger also. I think the charger may be "slipping" out of the lighter socket anyway ? Don't think it is the problem? Seems odd after the original battery went for 5 years that I went through 2 new batteries since then ? Thats what I get for not driving the car!!