1st day driving the Prius. Left headlights on for 5 hours, battery drained.

Always, always, always, lock the car. If you've left it running or the headlights on or a door or the rear hatch ajar it will give you a long warning beep.

 

you can override the auto shutoff by turning the lights off then turn them right back on when you shut down.

if you didnt do that then your lights did not stay on. i have FREQUENTLY come out from work after a 10 hour shift to see my headlight switch on and never had an issue. the car is too smart for that.

 

Just to expand on Evan's comment above, you can avoid the ajar hatch (or any other door) by always using the black button on the door to lock up. The SKS will protest if you try to lock with an open door.
But beyond that, if you want to turn the lights on for daytime driving, you need to train yourself to turn the lights off as part of the shutdown routine and to always look back at the car to be sure your lights are off.
Having said that, welcome to the wonderful world of Prius. You're still getting to know your car, so don't beat yourself up too badly about this.

 

i too had a WONDERFUL neighbor come knocking on my door to tell me i left the reading light on. nice guy indeed. couldn't thank him enough.

those are some of the features that i missed in my STS. everything would shut off, no matter what...................then the doors would lock the minute i put the car in gear, R or D. it would arm itself too...................***sigh***

 

So, if you haven't used your car for a week in the winter, and you suspect your 12V battery might be run down a bit, just press the power button and leave it on ready for 20 minutes? The big battery charges the 12 v battery?

I guess that means starting the car has nothing to do with the 12 v battery. It will start even if the 12 V is dead?

Do you have to keep your foot on the brake powered in the ready mode while charging the 12v battery? I guess not.

 

Yes, run it at least once a week for 20 minutes. The car keeps the 12V battery charged when the car is "Ready". You don't have to do anything special. If you are going to leave the car "Ready" but not drive anywhere, leave it shifted in "P". (If it's in "N" then the big traction battery won't get charged, and if the traction battery runs down that's a whole 'nother and much bigger headache.)

If the 12V battery is dead you will need a jump to start a Prius, same as in any other car.

 

I'd suggest giving the battery some margin by keeping the car READY for at least 30 minutes once per week. If the battery is dead and required a jump start, 2 hours would not be excessive.

The 12V bus is operating at ~13.8V when the car is READY, so the 12V battery will take longer to charge compared to regular vehicles whose alternators are operating at ~14.4V or so.