Screenshots delayed, low battery slows down laptop

Usually when I take a screen shot, the laptop does so immediately. But for a while, lately, my mac book pro is not taking screen shots instantaneously. The screenshot (shift cmd 3) is taken a few seconds earlier than when I press the keys, for a video. Also, my laptop slows down when battery percentage goes close to 5%. I am unable to change from Desktop 1 to 2 to 3 as fast as I could usually do. Is there any relation between these issues? What can I do to stop this problem?