With no key in, or with key in position "0" ( no turn ) you can run the lamps, and this will be off 12v battery only.

With key in, turned one click forward to position "1" you can run the lamps, radio, and windows, etc. This is "ACC" and runs off 12v battery only.

With key in, turned two clicks forward to position "2" you can now run everything in the entire car. This is "RUN" position, and this now draws power from the HV battery pack in the rear of the car. The car icon will not be lit unless you turn the key once more to "start" the car. With car icon off, the gas engine will never run.

If you leave your headlamps ( or radio, or whatever ) on with key in position 1 (ACC) you will only draw down the 12v battery.

If you leave your headlamps on with key in position 2 ( RUN ) you will draw down the HV battery first, and then the 12v battery second.

-John E