I drive my 2002 S430 once or twice a month. The last time was more than 4 weeks apart and the battery died.

What maintenance type charger should I hook up to the car so the battery will not die?

 

that battery is bad. i have a bmw that I don't start for 6+ weeks, turns over just fine. there must be some warranty on it.

 

I had a 2001 S500 wich I usead about once a month. The battery never failes to be flat, I was told by Mercedes Manhattan that it was to be expected. I simply bought a battery powered jump starter from home depot. I ended trading the vehicle for a 1998 Bentley Turbo R. Much less high tech but it always starts for me.