A couple of questions:
Did this happen after a reboot, or is it continuing consistently? It's normal (unfortunately) for the device to rescan your storage looking for new media files after a reboot. So if you have a lot of media files, it can use up a fair bit of battery after a reboot. Even given that, this seems pretty high.
I think the next most common issue that causes this is a corrupted nedia file or a corrupt directory on the SD card. If you have an SD card, unmount it, remove it, and reboot. If the problem goes away, then you have a bad file or directory. Copy eveything off the card to a computer, then reformat the card in the phone. If the problem comes back (unlikely) you've got a bad card. Assuming it's OK, then you might have bad file(s). You can do two things: copy everything back, and hope the reformat cured it, or you can copy them back a bit at a time, wait a day, and if the problem returns you know the bad file was in the most recent batch.
If removing the card didn't resolve it, then you probably have a bad file on internal storage. Copy all your media files to a computer, and delete them from the phone. Reboot, and see if that resolves it. If so, copy them back a bit at a time, as above.