Most iPads will use 10%-20% of the iPad's battery per hour. iPhone battery life will vary greatly based upon individual usage habits. To maximize your iPad or iPhone battery run time, ForeFlight suggests the following:
1: Close all other apps running in the background.
2: Reduce brightness as much as practical.
3: Turn on Airplane Mode when flying. This will disable all broadcast functions (Wifi, Bluetooth, Cellular Data) while leaving the internal GPS receiver enabled.
Note: You may need WiFi or Bluetooth turned on if you are using Sentry, an external GPS source, or a Bluetooth headset.
Adding an external charger will also increase the battery run time. However, some devices will continue to lose charge even with a charger attached. You can learn more about ForeFlight recommended chargers in our Buying Guide.