2004 DeVille Battery Dead After Two Days

Guys,

On Wednesday, we drove the car and parked it in the garage. My wife went out tonight to open the trunk and found that none of the interior lights turned on so it looked like the battery was completely dead. However, I did not check the battery voltage with a voltmeter to see what it actually was. I connected my 10 amp battery charger and turned it on. The battery started charging at about 12 amps (on the meter). After about an hour and a half, I disconnected the charger and checked to see if the lights worked, and they did. When I reconnected the charger, it continued at about 12 amps.

Any ideas on what could have discharged the battery after only two days? It's only 2 years and 9 months old, but I guess it could still be defective. I have a Schumacher digital battery tester that I can try when the battery is fully charged, but it looks like that will be quite some time...maybe tomorrow at this rate. In order to use the tester, I have to input the specified Cold Cranking Amps. Since the battery is under the back seat and my back muscles are currently incapable of doing any work does anyone know what the CCA rating of a Delco battery for this car is supposed to be?