[donv]

Vanessa, I think it's lighly likely you're going to need a new battery. A charged conventional car battery will not freeze even when subjected to ungodly low temps like -40, but a discharged battery could freeze at temps like you encountered. The act of freezing solid will usually either crack the case or break the plate structure inside the battery. In the first case, when the battery thaws you can end up with an acid leak (nasty!). In the second, the battery will have less or even no power (depends upon the degree of damage, whether it takes out just one cell or more).

The Optima battery that folks have mentioned here is a different design and does not have cells with an acid bath, in addition to the other benefits that have been mentioned. However, they are significantly more expensive than a conventional battery.