Just because Android apps have no “close” button doesn’t mean they shut down when you return to the home page or move on to another app. You calendar, note pad, and programs in which you turn on event notifications might periodically run in the background, depleting your battery. Download and run Advanced Task Killer Free. You’ll be amazed at the apps that run on start-up without your knowledge. While you can kill the task killer along with other apps, we recommend letting it run so you can easily use it a couple times throughout the day. Being able to set conditions for killing running apps would be an interesting future touch.