iPhone Duo battery rating changes with the screen users choose

Apple’s iPhone Duo has separate battery cells in its two halves, and the company gives different video-playback ratings for the inner and outer screens. MacRumors reported the figures on September 9 after Apple announced the foldable phone and described its dual-battery design.

Using the larger 7.6-inch inner display, Apple rates the Duo for up to 31 hours of video playback. Using only the 5.4-inch outer display raises the rating to up to 44 hours. The difference reflects the size and power demands of the two screens.

Apple’s typical-use estimate is up to 24 hours when the phone is used with both screens. The company says that calculation includes equal use of the inner and outer displays, along with messaging, photos, music, social apps, video, games, web browsing and navigation.

MacRumors said the two batteries operate as one system. That arrangement allows the phone to keep working as a single device even though the cells are split between the foldable halves. It also gives Apple more room to distribute components across the chassis.

Charging is part of the same product design. Apple says the Duo can reach 50 percent in around 20 minutes with wired charging and around 30 minutes wirelessly with MagSafe or Qi2. Five minutes of charging can provide up to five hours of outer-screen video playback.

The ratings are Apple’s controlled estimates, not a guarantee for mixed use. Brightness, cellular signal, camera activity, multitasking and app behavior will influence the result. A user who spends most of the day with the inner screen may see a different pattern from someone who keeps the phone closed.

Apple says iPhone Duo preorders begin October 16 and availability starts October 23. Independent reviews will show how the dual-battery architecture performs when the phone moves repeatedly between its open and closed modes.