Not normally, but you said you left it trying to finish for several hours, so that might have drained it. Also, the battery meter isn't completely accurate so it might not have been as full as it looked. Depending on which parts of PR1.1 succeeded, you may find you can't use the older firmware. Specifically, if the phone/3G firmware part updated, then the rest of PR1.1 must be used with it. But I don't see any harm in trying older firmware first, only that it might not work.