All batteries will eventually experience diminished efficiency, storage capacity and will need to be replaced. However, regularly recalibrating your Lithium-ion battery will help to prolong your battery’s life and health, which will help reduce the frequency with which you’ll have to buy a new battery.

Apple recommends recalibrating your battery at time of purchase and then every few months after that. Battery University recommends recalibrating your battery every 30 charge/discharge cycles.  For years, I had a repeating event on my iCal calendar that sent me an email reminder which included a copy of Apple’s instructions. Recently, I started using Watts (30-day free trial, then $6.95) which lets me monitor the health of my battery, reminds me to calibrate my battery, then guides me through it.

Apple indicates that one should expect current Mac laptop batteries to retain 80% of their charge capacity after 1000 full charge/discharge cycles. Watts lets you keep an eye on this and alerts you if your battery is unhealthy and needs to be replaced. If you have the Growl notification application installed, Watts can be configured to display useful notifications and reminders to recalibrate your battery. I recommend Watts. Check it out, you might find it helpful.

Here’s a copy of Apple’s current instructions for recalibrating your battery if you own a MacBook, MacBook Pro, MacBook Air or PowerBook G4 with a dual-layer DVD drive.

• 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.

Personally, I find it inconvenient to try to incorporate the above recalibration process into my day-to-day use of my laptop. Thus, I tend to do this on a Friday evening, when I’m done using the computer for the night. I save all of my documents and quit all applications on the laptop. Then, I open a QuickTime movie and set it to loop continuously. I then disconnect the power cord so the laptop is running on battery. Sometime during the night, the laptop’s battery will be depleted and the laptop will automatically go to sleep. Then it can sit there for a number of hours. On Saturday morning, I”ll connect the charger to charge it up, which can take a couple of hours. When I’m ready to use the laptop the battery is fully charged and ready to go.