The other day I noticed my current battery capacity was around 65%, which for a MBP under a year old I was a little annoyed at. According to iStat Nano, a [excellent] system monitor widget and confirmed with Coconut Battery the maximum battery charge I could currently hold would be around 3500mAh instead of the factory default of 5500mAh.After a quick search on the Apple site I have managed to bump it back up into the 90% region. How? Easy, I Calibrated the battery, something you should do every 2 months or so!.
Plug in the MagSafe power adapter and fully charge the MacBook or MacBook Pro battery until the light on the MagSafe connector changes to green and the Battery icon in the menu bar indicates that the battery is fully charged.
Allow the battery to rest in the fully charged state for two hours or longer. You may use your computer during this time as long as the power adapter is plugged in.
Disconnect the power adapter with the computer on and start using it with battery power. When the battery's charge gets low, you'll see the low battery warning dialog on the screen.
Continue to keep your computer turned on until it goes to sleep. Save your work and close all applications when the battery's charge gets low and before the computer goes to sleep.
Turn off the computer or allow it to sleep for five hours or longer.
Reconnect the power adapter and leave it connected until the battery is fully charged. You may use your computer during this time.
Watching the health go up after this made me breath a sigh of relief!I know I've got a MBP pro but I believe this should work with most batteries except for Li-Ion where I believe deep charging will actually shorten the life. But before you do try this make sure you consult to the manufacturers guide.