Fix Battery Drain Issue with the iOS 7
There have been reports of some iPad users having massive battery draining issues after updating to iOS 7. iPads affected by this issue will last no longer than a day. The issue does not have to do with leaving the wifi or bluetooth on, in fact it is much simpler than that.
On some devices after updating to iOS 7, the Auto-Lock option gets changed to Never. That means your screen is always on. It may look like it is off, but in fact it just dims after a certain amount of time if left a lone. You will need to change the Auto-Lock setting to fix the issue.
Fixing the Battery Draining Issue on iOS 7
1. Go to Settings > General > Auto-Lock
2. Change the Auto-Lock to the desired setting. (2 minute is recommended; the faster the screen is off, the more battery you will have)