The EMS widget is looking at pin 2 on the EMS DB37 connector, not the SkyView display's DB37 connector. So without doing some active wiring between the SkyView DB37 and the EMS DB37, you won't see a voltage on the EMS page. The only way to see the internal battery voltage at the moment is through the screen hardware information, though a more persistent indicator is on the list of things to implement in a future firmware version.