About a month ago I took the car out for a drive.  Everything ran great, made several stops, nothing unusual in regards to starting or running.  Parked it in the garage and it sat for about two weeks.  A week or so ago thought I'd take my younger daughter to school in it and then drive it to work.  Tried to start it - nothing.  Not even a solenoid click.  I think battery voltage was only like 2 volts or something.  Put the 2 amp charger on it for a couple of days and the green light came on indicating everything was A-OK.  But voltage was only showing 11.5.  Enough to turn the motor over 1/2 turn, but that was it.  The battery is less than a year old, it's an interstate from Costco.  Just a battery or something worse?  I could go get a new battery from Costco, but probably not an effective method of troubleshooting.  Major electrical drain?  My factory alarm system does work (at least it did) but I know they can be problematic with drain.  Until now I really haven't had any drain problems - car could sit for two months and still start no problem.  Alternator or regulator?  At a loss here.... thanks

You will need to disconnect the battery and put a volt ohm meter between the cable and the battery terminal and measure the current draw when everything is off. If that is just a few milliamps, then your battery is probably bad. You can take your battery to most auto parts stores and get it tested for free though before you return it.

Charge the battery, and then take it to have it tested. It has to be fully charged to get a reliable test result. A lot of things on these cars can drain a batt overnight, or over a few days, including the clock, a bad alternator, interior light left on, the alarm relay, etc. Start with the basics, and verify the battery is good before doing anything else. 

Thanks guys. Battery on charger now (again) and will take it. In this weekend to have it tested . We shall see !

Dave - +1 on getting the battery tested then testing the system for draw with an ohm meter. Usually any kind of spark when you connect the last cable is a good indicator of current draw. 

Once you've determined the battery is good, disconnect the negative battery cable and run a test light between the negative post and the cable end.  The test light should illuminate.  Then remove one fuse at a time until the light goes out.  When that happens you've isolated the circuit the battery drain originates from.  Then you can determine what part of the circuit the problem lies.

Thanks, John.  I've had a cut-off switch installed for several years now (it's actually a decent one) but I don't typically have to use it, even if I won't drive the car for a month.  Going to be looking for some sort of drain.  

Thanks - yep I know about the concerns about testing current draw with the multimeter.  Mine you have to move the red lead to a different terminal if you want to test on the 10A setting.  Even then if it's drawing anywhere close to that you can only let it operate at that current for a matter of seconds, I think.  Will be careful...thanks.  

No courtesy light timer on mine.  It is possible the interior lights were on all night, but it's unlikely.  It's parked in our garage right now where I see it all the time at night versus my shop where it usually lives.  But possible.  Doesn't take much for a door switch to fail and go to ground which turns on the lights.  Alternator is definitely a possibility too.  It's a reman that I bet is more than 10 years old.  Or the alarm relay.  Or something else.  Or it could just be the battery with no drain.  I'll be looking into it later this week.  Thanks for the suggestions.