Hi Greg, The manual for your PowerBook probably stipulates that you must calibrate your battery within its first week of operation, and maybe periodically (check the manual for details). This is typically of Lithium Ion batteries (e.g., mobile phones are supposed to be recalibrated periodically to prevent them cutting out unexpectedly). From the sound of it, you battery does not know its "full" and "empty" capacities. To fix this, recalibrate it according to the PowerBook User's Guide (or buy a new battery).
FYI The PowerBook has various low-power modes: low power warning; normal sleep; hibernate; abrupt power failure. Your battery has been progressing from hibernate down to abrupt power failure as the un-calibration gets worse. James.
