Calibrate your Mac battery
I got this directly off Apple’s website.
Apple does not recommend leaving your portable plugged in all the time.
You can calibrate your iBook, PowerBook, MacBook, MacBook Air, or MacBook Pro
computer’s lithium ion battery for best performance.
The battery calibration for the PowerBook G4 (15-inch Double-Layer SD) and any
model of MacBook or MacBook Pro has been updated because of a new battery
released with this computer. With these computers, follow these steps to calibrate your battery:
- Plug in the power adapter and fully charge your PowerBook’s battery until the
light ring or LED on the power adapter plug changes to green and the onscreen
meter in the menu bar indicates that the battery is fully charged. - Allow the battery to rest in the fully charged state for at least two hours.
You may use your computer during this time as long as the adapter is plugged in. - Disconnect the power adapter while the computer still on and start running the
computer off battery power. You may use your computer during this time.
When your battery gets low, the low battery warning dialog appears on the screen. - At this point, save your work. Continue to use your computer; when the battery
gets very low, the computer will automatically go to sleep. - Turn off the computer or allow it to sleep for five hours or more.
- Connect the power adapter and leave it connected until the
battery is fully charged again.
Tip: When the battery reaches “empty”, the computer is forced into sleep mode.
The battery actually keeps back a reserve beyond “empty”, to maintain the
computer in sleep for a period of time. Once the battery is truly exhausted,
the computer is forced to shut down. At this point, with the safe sleep function
introduced in the PowerBook G4 (15-inch Double-Layer SD) computers,
the computer’s memory contents have been saved to the hard drive.
When power is restored, the computer returns itself to its pre-sleep state using
the safe sleep image on the hard drive.