1. With the BB connected to the power wall, remove the battery
2. Wait 30 seconds, you should see a red light during that time
3. Put the battery back, and then it should reboot back to the normal BB home screen. You may notice that the battery sign is red (completely drained). By the way, if the BB does not come back after you put the battery back in, and you wait a few seconds, press the power button.