I have an iPad 3 Retina with the newest iOS 7. Sometimes, not always, with all apps closed and the iPad turned off something is completely draining my battery. Is there any way to see what is causing this? It is especially annoying when I have shut it down with, say, 80% battery left and when I need to check something I turn it on only to discover that I have to do a whole new recharge. Thanks for any help on this.