I have a PB G4/400 thats about 1 1/2 years old and recently I've been having battery problems. My battery only lasts about 40 minutes and the gauge is often very inaccurate. I'll be running at 100% charged, then after 10 mins it will jump down to 40%. It then jumps to 0%... the funny thing is the PowerBook will then run for half an hour at 0% before going to sleep. Are there any tricks I can try to squeeze more life out of my battery? If it's gone, any places to get a cheap PBG4 battery?