It's between -35 and -40 F. (Have used '07 Prius, 30 K miles & no manual except the small pamphlet) 1. Plugged it in 2 hours. Started & idled for 20 min while scraping windshield & running defrosters. 2. Drove to have new tires put on in a shop and then it was dead in the garage bay. They jump started the 12 volt under the fuse box in front. 3. Drove again & parked, plugged in. Three hours later, totally dead. 4. Dealer swamped - says jump it and leave it to freeze outside at the dealership & they may get to it in a week. Question: Is the battery under the hood the famous 12 volt? If so, what is the battery in the rear of the car that I've heard of. I guess they will take out that front battery, test, tighten connections, etc. and either say it is fine, put it on a charger, or sell me a new battery. Are these reasonable assumptions on my part? Question: what do you think happened? Did I do something wrong as stated above at the beginning of this post?