Finally figured out the mystery of the dead battery. Ever since last October my battery on the Mercedes pens kept dying and last week I finally had it having to get a battery jump at the post office. At first I though I had a short in the electric system, but the problem persisted. I finally rolled up my sleeves put on my rubber gloves and crawled under the hood and took out my alternator.
First loosen the two 17mm bolts holding the alternator in place, then loosen the 13mm nut on the alternator adjustment plate. Take the screws out and slip the two belt off. Put the alternator on the bench and examine. It turns out the voltage regulator was to totally worn out and in need of a new one. Monday I will be taking this entire unit down to a shop to be rebuilt.