I drove my 2005 Prius to work and parked, left it overnight, then the next night went to take it home and the fuel and gear lights are blinking, and the car won't start. Any help?
Unknown - I've had the car for 1.5 years, so at least that. I'll put a volt meter on it and check it out.
^^^ Make sure you check it either right after you're in the bad state or after the car has sat overnight or MANY hours (BEFORE you put the car into READY mode). If it's still the original, it's almost surely toast.
3.1 volts, no idea how it ran down like that. Got a jump and got home, battery is on a trickle charge, but I take it I should get a new one? Does anyone know why it drained down so fast like that?
^^^ Wow! If it doesn't hold a charge, you're definitely due for a new one. BTW, the Prius has no dedicated starter motor and the ICE (internal combustion engine) isn't started by the 12 volt. So, you will NEVER have symptoms of a starter being slow to turn or be unable to turnover. Instead, weird stuff like the above happens.
The car won't start without the 12 volt battery, but the 12 volt battery doesn't power the starter? I really don't get where they were going on this one. I ordered a new battery and put the car on trickle charge for the night.
Yep. Search for 12v in http://www.autoshop101.com/forms/Hybrid02.pdf along with starter in http://www.autoshop101.com/forms/Hybrid01.pdf. The engine is started via the big HV battery powering MG1.