Battery drains when car not used in 2 weeks
1996 A4, 2.8L V6 TPI SOHC 12V FWD. ~120k miles. Original battery from when problem arose was bought from Walmart, a MAXX-48 with 700 CCAs. Replaced once for the same battery. Now replaced for a MAXX-H6 which has 770 CCAs.
The same thing has happened twice. I didn't drive the car for like a week or two and then I go to start it and the battery is dead. This most recent battery that died was put in only 2 months ago. I only noticed the problem after I had a repair done by a shyster mechanic, who blew a bunch of fuses when replacing my ignition cylinder. I assume they did not disconnect the battery when doing their work, which is why I had a bunch of blown fuses.
Any way, I checked all the fuses last time I replaced the battery and could not find one that was draining power. The lights were not left on, and this battery was so dead I couldn't even get a millivolt reading on it. What do you think is going on? How can I test this to find the problem or drainage source?
Thanks for the help in advance! I am new to the forums and I appreciate the hospitality and help.