Go into your Settings Menu and turn off Location Services and Blue Tooth. Then put your device in Airplane Mode, which will also turn off the Wi-Fi, so you have to turn the Wi-Fi back on for the Navigator to communicate with Expedition.

Next turn down the Brightness as much as possilbe for the light conditions you are sailing in. Using Night Mode does draw slightly less power because of the black background, and offers great visability on all but the brightness days. I actually prefer it most of the time.

Finally turn off all programs that are running in the background except for the Ventus Navigator. If you aren't familiar with this feature you start by double tapping the built in round button. This will bring up a bar across the bottom of the screen that shows all the programs that are running in the background. Tap and hold any one of them untill they start vibrating slightly and have a red circle with a minus sign in the upper left corner of each icon. Then tap each icon to close the program. When you have close all but the Navigator tap the round button twice to return to your home screen.