New Battery goes dead radomly
 

I have a 99, 93 turbo convertible,manual trans, it runs like a top,but, at times the battery will be drained to the point it won't turn the engine over! The battery is new too. Every so ofter the alarm system will go off for no reason at all,(the car is locked). I've noticed this tends to drawl the battery down when this occurs and the Saab tech can not find a drawl to explain this. The battery drawls down at times with car unlocked and no signs of the alarm going off. Does anyone have any advice or heard of this before. I am getting ready to pass the car onto my daughter, but have apprehensions. The car sat for over 2 weeks in the garage unlocked and started right up??? Is there anyway I can test for drawls myself? ANY help would be appreciated. Thank you