Re: batteries and severe cold
Better off with a Hybrid in the cold.
More overall battery power with less dependence on individual cells to deliver the necessary power to start the ICE means much higher reliability as compared to a vehicle that relies on a small number of cells, such as any typical 12v car battery. A Prius doesn't use the 12v system to start the ICE, so there's much less chance of a failure to start when viewed from a probability of failure due to extreme cold (lowering the effective output capacity of each cell) when the battery is made up of more cells. There is another factor though, the reliability of the cell connections, and Toyota has addressed this in the Prius I, as a recall to clean and re-seal the battery due to some corrosion, so as long as the battery is properly sealed where needed when there's condensation it's fine, and I would assume they addressed this completely in the Prius II.
Also consider the efficiency of starting the ICE with an AC motor rather than a small DC motor as in a conventional car, and the likelyhood of a mechanical failure in the "starter" is much less, and found to be very reliable. Also consider that the high voltage DC is converted to AC, and in effect regulating the voltage as necessary, so the available power of the battery is not usually fed into the motor, so even at very "low" battery voltage it's possible to still crank out significant amounts of power to the wheels, but depending on how "low" the battery is the computer will not let you drain it that much, for it knows it always need enough to restart and keep the battery healthy.
In general a Prius will keep the battery within a healthy range of charge and discharge for optimum functionality, and the computer keeps track of everything so any early symptoms of battery failure are recorded and you'll be alerted, whereas there's no warning or monitoring of the battery in a normal car, except perhaps luxury mobiles, but I wouldn't know, not owning them. The batteries are also said to be lasting longer than they first predicted when they were introduced in Japan in the 90's. That's good news in general because since those initial batteries there have been significant improvements within the same type of battery, such as the large Prius II battery. I think they will last at least as long as people generally keep "new" cars for, these days 10-15 years is typical of the people that hold onto a car, and that what's being predicted, at this point for battery life of the first generation batteries.
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