Apple's fourth developer beta of iOS 27 includes code references to an iPhone with two internal batteries, offering the strongest signal yet that the foldable iPhone Ultra will use a dual-cell design.
Macworld's Filipe Espósito spotted the new Battery Health strings, which replace singular "battery" language with plural phrasing. "The batteries in this iPhone are performing as expected," reads one string.
Another warns that "the health of the batteries in this iPhone has significantly degraded."
Current iPhone models show only single-battery messages in Settings. The plural wording is exclusive to iOS 27 beta 4 and appears alongside existing single-battery references, confirming Apple is building software support for a multi-battery iPhone.
Foldable smartphones from Samsung and Google already split battery cells between the two halves of the device. The iPhone Ultra is expected to follow the same approach, with one battery in each side of the fold.
Regulatory filings previously pegged the Ultra's two cells at 1,921mAh and 2,962mAh, combining for a 4,883mAh total. By comparison, the iPhone 18 Pro Max is expected to pack a larger single cell, with regulatory filings showing capacities of 5,391mAh in China and 5,567mAh in the U.S. The iOS 27 code also hints that each battery could be serviced independently. Replacing a single degraded cell rather than the entire battery pack could lower out-of-warranty repair costs, a meaningful difference for a device expected to carry a premium price tag.
Weibo leaker Digital Chat Station first flagged the dual-battery design earlier this month. The iOS 27 beta code corroborates that claim with concrete software evidence.
Apple is expected to unveil the iPhone Ultra this September alongside the iPhone 18 Pro lineup. The foldable is rumored to feature a 7.7-inch inner display and a 5.3-inch cover screen, with the dual batteries split across both halves of the device.
