The battery on my iBook has got some weird problem 2 days ago, and so far I still have not found a way to solve it.
Well. The battery still works fine - it still gives me around 3-4 hours of usage with good brightness and airport turned on. The problem is actually on how Mac OS X reads the amount of juice still left in the battery. First of all, it does not calculate the remaining time properly. When I ask the power metre to show the remaining time, it just displays "(Calculating...)" and then that's it. If I open up the system setting, it will then tell me that there is still 19:46 left in the battery - 19 hours and 46 minutes!! And of course the iBook won't last that long. The percentage will drop slowly, and then after 4 hours of usage when the metre still reads 80%, iBook will then suddenly turn to sleep. Weird.
I've tried to calibrate the battery according to that Apple document, but it does not work. I've tried to reset the PMU, but nothing has happened (Actually the combination of Shift-Ctrl-Option-Power simultaneously is quite hard - reminding me those special movies in those arcade boxes. Since I'm not good at games so maybe it did not really reset the PMU). There are some even more complicated procedures that I've tried, but the battery estimate still can't finish calculating. There is one more solution that I've not yet dare to try - short the PMU circuit on the battery. I found this news group post, which has exactly the same symptom as mine, not very helpful either, except the fact the Apple has acknowledged it but cannot provide solutions (besides ignoring it).
It still works, but just annoying that your computer goes to sleep in front of you when the battery metre still shows 80% left...