If you have a HD HERO Original camera, you may need to download new firmware using the Battery BacPac. 

If the number 2 does not appear on the front status screen when the Battery BacPac is fully charged after being attached to the camera. Please update your HD HERO Original camera's firmware and follow the instructions to upload the new software to your camera. 

The HD HERO2 does not require a firmware update for the Battery BacPac to function properly.