I have a 7 week old 12" PowerBook. Yesterday I bought a new battery at my local Apple store to double the amount of time I can be away from a charger. I popped it into my PB when I got home and it had a 42% charge. So I used it until the battery completely died, put the PB on the charger and went to bed. This morning when I woke up I could hear the PB's fan whirring full blast. I sleep in the same room as my PB every night and it's always been silent. I picked it up and it was SUPER hot and it would not power up. So I put my original battery back in. This time when I hit the power button I could hear something going on in the PB. I assume the hard drive spinning, but I'm not sure? I ended up resetting PMU and it started right up. Questions... did the new battery do this? It's an Apple battery. Why were the fans going full blast this morning when the computer was off when I put it on the charger? And why was it so hot? Could this have been caused by anything else and it was just a coincidence that it happened with the new battery? Any insight at all? Also, is there any way to charge the spare battery WITHOUT putting it in the PB? Thanks.