I had my battery drain over night twice to zero. From what I read at a full drain can make the battery no longer take a charge unless it is reconditioned. (something you can't do at home) Both times I had left it plugged into a usb cord because of using internet pass through. The first time to my turned off computer and the next time I remembered to unplug it from the computer but left it on the cord. To my surprise it drained even then. Since then I have rooted and I left it on the cord and plugged into my off computer over night and it did not drain. It was at 98 % when I got up. So, score 1 for rooting. I will have to research but I think it could be the new radio I loaded.