Some people have a habit of removing the battery from the laptops when they’re using it in the hopes that it will result in more extended life for the battery.
But it looks like this practice is not a good one if you’re a MacBook or MacBook Pro owner. Benchmarking tests revealed that a huge performance hit happens when you use these Apple laptops without the battery. This is apparently indicated in the Apple website, which states that this happens as a way of preventing the laptops from shutting down if for some reason the units try to get more power that the A/C adapters alone can provide.
So the lesson is clear, leave the battery intact when you have a MacBook or MacBook Pro. Jury’s still out though on what happens if you already have a dead Apple battery.