My wife phone did this. Check in the battery settings and see what process is using up all the battery.
On my wife's phone it was the media process. Seemed to get stuck on an iffy corrupt jpg file from when her SD card was in her blackberry.
Try removing all the files from the storage by just dragging them over to your computer and see if it it fixes the issue.
I formatted both the SD card and internal storage and replaced the folders and the problem went away.