Simple Just disconnect the Battery say for a Month hook it back up and it should be Still fully charged and start no Problem , Evan 2 or 3 months on a good battery .

That's a good short test , So once your convinced you have a short just find it

( if the Battery go's dead / down that fast you should be able to see it arc when you Hook it up most likely, your clock is not going to kill the battery in a week or more )