Is this a plausible symptom of an aging / dying / messed-up battery, or should I be looking for other solutions?
Computer: 12" G4 PowerBook (original version), 21 months old, running 10.3.7 (problem started with 10.3.6).
Symptom: When the battery level reaches approx 30% full, 0:45 left,
it suddenly changes to 0%, and the machine immediately shuts down
just as if the battery really were at 0%. When I plug in the
charger, recharging seems to be from zero. But I haven't expended a
batteryful of power; this machine used to make it through a 2-hour
class with an hour of power left over, and now it can hardly make it
through the first hour, with the battery's remaining time sometimes
counting down faster than real time.
Not a PMU problem: I've tried the obvious stuff -- resetting the Power Management Unit, and calibrating the battery as per Apple's instructions.
I would be grateful for any suggestions.