Code discovered in the fourth developer beta of iOS 27 contains battery health strings written specifically for iPhones with more than one internal battery, a configuration that does not exist on any iPhone currently on sale.
The strings read: “The batteries in this iPhone are performing as expected” and “the health of the batteries in this iPhone has significantly degraded.”
A third string addresses a scenario where “one of the batteries” may not be a genuine Apple component, triggering an authentication warning. Every iPhone sold today has a single battery, so the software has no current hardware to run on.
What a dual-battery iPhone would actually mean for users
Book-style foldable phones split their batteries across both halves of the device, one cell on each side of the hinge.
That approach exists because the hinge mechanism consumes space that would otherwise hold a single large battery.
Samsung, Google, and other Android manufacturers building foldables have used this architecture for years. Apple appears to be engineering the same solution for its own foldable hardware.
For owners, a dual-battery setup changes how battery health tracking works. Instead of checking one percentage, users would monitor two separate cells.
Apple’s new strings suggest the Battery Health screen will display combined status, but will also flag individual cell degradation and flag non-Apple replacement parts on either cell independently.
iOS 27 has been building toward foldable support since its first beta
The battery strings are not the first foldable-related code found in iOS 27. The initial beta released earlier this year included references to fold states and angle detection, suggesting software support for a hinge that bends and holds at different positions.
Apple has also pushed developers to update their apps to handle variable screen dimensions, which matters far more for a folding display than for any existing iPhone form factor.
Supply chain reporting has separately and consistently described Apple’s first foldable iPhone as using a dual-cell battery design. The iOS 27 code aligns with those reports without being sourced from them.
The device is referred to in various reports as the iPhone Ultra. Apple is expected to announce its fall iPhone lineup in approximately two months, with the foldable model widely anticipated to be part of the announcement.
Software strings found in developer betas do not guarantee a product ships, but the volume and specificity of foldable-related code appearing across multiple iOS 27 betas is greater than what typically surfaces this far ahead of an unconfirmed product.
