Your car, in its stock configuration should easily wait over a week without significant battery loss.

If it were mine I would look at voltage drains from an after market alarm and a stereo with external amps. Often these amps are hooked up and left on continuously.

To check your drain, use a volt-ohm meter at the battery. When the key if off you should have just a tiny current flow for say, your radio head station setting memory.

Haasman

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'03 E320 Wagon-Sold
'95 E320 Wagon-Went to Ex
'93 190E 2.6-Wrecked
'91 300E-Went to Ex
'65 911 Coupe (#302580)