Replacing the Battery
If your MacBook Air’s battery won’t charge, or if it runs down very quickly when you’re running without outlet power, it’s time to yank out the old battery and replace it with a new one. On other Apple notebooks, such as the PowerBook, iBook, MacBook, or MacBook Pro, the battery is what Apple describes as a user-installable feature. That’s because on all those models, it’s fairly easy to remove the existing battery and replace it with a new one. They all include some kind of latch or lock that you can easily release to get at the battery.
Unfortunately, that’s not the case with MacBook Air, which doesn’t come with a battery-release mechanism. Instead, you must remove either 15 or 19 (depending on your version of MacBook Air) screws to get at and release the battery. It’s not exactly something routine you’ll do on the morning train, but it’s not difficult either — just tedious.
I should warn you that opening the case technically voids your MacBook Air warranty, if it’s still in effect.
Working with a third-, fourth-, or fifth-generation MacBook Air
Actually, I should say that it’s not difficult if you have a first- (2008) or second-generation (early 2010) MacBook Air. I’ll show you how to replace the battery in those versions in the next section.
Things are quite a bit trickier with the third-generation (late 2010), fourth-generation (mid-2011), and fifth-generation ...