Another item to be concerned with is if you have a sunroof, make sure the rear seat overhead reading lights are turned OFF. -- They are NOT a 20 minute timer as the other lights are.

 

An 09 should not need a new 12-volt battery, yet, even Michigan. Those AGM batteries don't suffer from warped plates, which is the most common cause of failure in standard wet-cell batteries. They do eventually fail, but it takes several years of operation.

My guess is you didn't get the car completely turned off. Even when completely off, there are some devices (such as the key-fob radio) that continue to draw power. That's why Toyota recommends not leaving these cars parked for more than 4-5 days at a stretch. But most people have no trouble with 1-2 weeks of parking. You just have to be careful that it is really turned off, including all of the accessories and lights. Check the back-seat overhead lights after every time you carry a back-seat passenger -- they really do not turn themselves off.

I have a truck that likes to drain batteries. Something about the way the alarm system works, I think, but they couldn't find the issue. I park it for weeks at a stretch, but it will drain its battery in just a few days. So I got one of those trickle-chargers, and leave an extension cord laying on the driveway next to where I park that one.

 

I traced my problem back to the Garmin Nuvi GPS mount plugged into the cigarette lighter.

 

Unfortunately, I don't believe this is the possible cause... unless you have re-wired the socket. I believe that the TCH's "cigarette lighter" isn't hot (there is no power supplied to it) when the ignition is off. Not sure how this could have caused a draw.

I leave our Garmin plugged I all the time, and it shuts off automatically when the car is turned off....

 

My sockets are dead if the power is off also.

 

I don't understand it either but my 12V battery kept dying until I left the Garmin mount unplugged.