With repeated charging and draining, the battery in your MacBook or MacBook Pro will lose its capability and eventually die. If you are using Apple notebook computer as desktop replacement, you might be tempted to take out the battery and run your MacBook or MacBook Pro using just the AC power. This will save you some money from buying a new replacement battery soon, but Apple has a build-in ‘feature’ in its MacBook and MacBook Pro: [Mac reduces processor speed when battery is removed while operating from an A/C adaptor](http://support.apple.com/kb/HT2332).
If the battery is removed from a MacBook or MacBook Pro, the computer will automatically reduce the processor speed. This prevents the computer from shutting down if it demands more power than the A/C adaptor alone can provide.