If you have your headlights on Auto and then drop off your passenger and stay in the car yourself, the headlights don't turn off. If you're waiting in the car for your passenger to return (say, after a doctor's appointment), your headlights could stay on long enough to kill the battery.

 

Thanks. Interesting.

 

Just turn them "off" for an instant then back to "auto". The lights will stay off until the next time the car is started. I do this when I'm working on the car in the garage, and don't want the lights coming on every time I open the driver's door.