After intermittent issues of rapid battery drain, I finally isolated the problem. My phone is charged every night and the charge usually lasts all day. Occasionally however my phone would completely discharge in less than 4 hours. I finally found that this occurred when I didn't completely exit "TuneIn Radio". If I just stopped the play the program evidently continued and caused battery drain. Usually I exited from the app but occasionally I would just stop and go to another task causing the frustrating intermittent problem. Don't know if this is the case with other radio/music apps but hope others can be helped by this post.