I love my 2010 Prius III. Brand spanking new. Had it since fall. I came home from work last Friday. Parked it in the carport, not the garage. It got pretty cold but not super cold. Went to get something from the car on Saturday, but didn't use it. Monday morning the battery was dead. Read the instruction booklet on how to jump start the car. Started using the battery charger. Everything went well. I wondered why the battery died. Maybe I left a light on. But aren't they supposed to turn off by themselves?
Yea, must be that you got a crappy battery. It happens, just getcha self a new one. It should be ok. If it happens again then there may be some odd problem that the dealer can diagnose. (The dealer should be able to replace your battery too under warranty.)
The headlights will turn off by themselves but the interior lights will not. If you left a door ajar it will not turn off the interior light. Most of the dead batteries I have seen reported in this site had to do with doors left ajar or interior lights left on.
If you leave a cab light on, they will stay on forever or till the battery dies. The head lights will trun off after 30 seconds but only if you turn them on in a certain sequence (I can't remember how that goes).
Americans don't get the auto. headlights. If you leave the light switch on (American car) the headlamps will go out after you leave the car, BUT, you MUST open the drivers door. Be warned, if you stop and wait for someone, and don't open the drivers door, the headlamps will stay on. Some people have drained the 12V battery this way waiting for someone for a few hours (listening to music, texting, etc.). If you leave the car in "Ready" mode it isn't a problem, but in "Accy" it is! Funny, my spell checker doesn't recognize "texting" as a word.
Folks, I've said it before but I'll say it again just one more time - so please PAY ATTENTION! I have a plain vanilla 07 Prii and I have verified this: If you leave any door ajar, the interior lights WILL turn off in approximately 20 minutes. If you leave a reading light on, it will stay on and kill your battery regardless what you do with the doors. Also, if you leave the trunk light switch in the on position, it will not turn off when all doors are closed. So there, I feel much better now! Oops, wrong about the trunk light, it will off with trunk closed. But if you leave the trunk lid ajar and the light switch is on, trouble lies ahead. The interior light turn-off fairy may not save you.
Now that you mention it, I might have left the driver door slightly ajar. Or I might have left the light on in the car. Or both. I noticed that the driver's side reading light was on after I started up the car.
Lock the car upon exit, as it will warn you and fail to lock if you have left something on or ajar. Just make it routine to lock even in the garage.
