Other Category problem
1985 Mercedes Benz 300sd V8 Two Wheel Drive Automatic 180000 miles

My 1985 Mercedes-Benz 300SD Turbo Diesel keeps needing a jump start or battery charge. I purchased a new battery and the car ran fine. However, if the car isn't driven at least every other day, the battery goes completely dead. I've checked all the lights, etc. to make sure they are off, but my battery keeps getting drained. Any ideas on what could be causing this?

Thanks!