It is strange that home screen and lock screen used up all my battery. I haven't used my iPad for around half a day and the last time I used it, it had around 60% left. I placed it aside on a table and didn't notice it for half a day. Then, it has only less than 30% left and the iPad is warm. It is iPad Air 2 running iOS 9.2, purchased 2 months ago. Is it defective device or software bug?