Apple has released iOS 27 beta 4 today, and a deep dive into the code has revealed intriguing references to a new iPhone model equipped with multiple batteries. This discovery strongly aligns with earlier rumors that the upcoming iPhone Ultra will feature a dual-battery design—a significant departure from the traditional single-battery architecture seen in all previous iPhone generations.
The code strings explicitly mention a "multi-battery iPhone" in the context of battery health monitoring. One string reads: "The batteries in this iPhone are performing as expected," while another states: "The health of the batteries in this iPhone has significantly degraded." These phrases are strikingly different from the standard single-battery references found in current iOS versions, confirming that Apple is actively developing software support for a device with multiple power cells.
What We Know About the iPhone Ultra's Battery Configuration
Earlier this month, a leaker on the Chinese social media platform Weibo, known as Digital Chat Station, claimed that Apple's forthcoming foldable iPhone—tentatively named iPhone Ultra—would contain two separate internal batteries. At the time, the claim seemed plausible given that many foldable smartphones from rival manufacturers already employ dual batteries to maximize capacity and optimize space. However, this new evidence from the iOS 27 beta 4 code provides the strongest confirmation yet that the feature is real.
Further substantiating the leak is a recent regulatory filing that details the exact capacities of the two batteries: 1,921mAh and 2,962mAh, for a combined total of 4,883mAh. This is notably larger than the battery in the current iPhone 16 Pro Max, which is around 4,400mAh. The increase in capacity would be welcome for a device that is expected to feature a larger foldable display and support for multiple screens, as previous code leaks have suggested.
The dual-battery design is not merely about higher capacity. In foldable phones, two batteries are often arranged on either side of the hinge to balance weight distribution and allow for a thinner form factor. Apple is likely taking a similar approach, enabling the iPhone Ultra to house a larger overall battery without making the device bulky. Moreover, splitting the battery into two cells can improve charging speeds and thermal management, as each cell can be charged independently or in parallel.
Historical Context: iPhone Battery Evolution
Apple has incrementally improved iPhone batteries over the years, but has largely stuck with a single-cell lithium-ion design. The iPhone 4 introduced a 1,420mAh battery, while the iPhone 6 Plus jumped to 2,915mAh. More recent models like the iPhone 14 Pro Max reached around 4,323mAh. The shift to dual batteries would mark the most radical change in iPhone power systems since the device's inception.
The move is also driven by the unique challenges of foldable displays. Unlike traditional slab phones, foldables have two halves that must accommodate hinge mechanisms, flexible screens, and other components. Using two separate batteries allows engineers to better utilize the available space, packing more total watt-hours into the device. Industry analysts note that Samsung's Galaxy Z Fold series has used dual batteries since the first generation, with capacities around 4,400mAh to 4,500mAh. The iPhone Ultra's 4,883mAh would give it a competitive edge in battery life.
Software Implications: Battery Health Monitoring for Two Cells
The code strings found in iOS 27 beta 4 are not just placeholders—they reflect Apple's efforts to adapt the battery health management system for multiple batteries. Currently, iOS provides metrics like maximum capacity and peak performance capability for a single battery. With dual batteries, the system must track the health of each cell individually and present a unified readout to the user. The strings suggest that the system will report the health of "batteries" collectively, possibly by averaging or combining the two values.
This is crucial for maintaining user trust and ensuring that the iPhone Ultra meets Apple's high standards for longevity. The degraded health string indicates that users will be warned when the combined battery performance drops below acceptable thresholds, prompting a service recommendation. Apple has been refining its battery health algorithms since iOS 11.3, and this update will likely extend those capabilities to a multi-cell configuration.
What the Multi-Battery Feature Means for Accessories
While the article mentions a list of accessories like AirPods Pro 3 and MagSafe mounts, the arrival of a dual-battery iPhone could influence the accessory ecosystem. For example, wireless charging pads may need to handle larger power demands, and car mounts might require stronger magnets to support a heavier device. Fast charging accessories could also benefit from the parallel charging capability, potentially enabling higher wattage than current iPhone models support. However, it's too early to tell if Apple will adopt faster charging standards or if the dual cells will be charged sequentially.
The iPhone Ultra is expected to be unveiled in early September, alongside other new devices. With iOS 27 beta 4 now providing concrete code evidence, the multi-battery feature seems all but confirmed. As the beta cycle progresses, more details may emerge regarding how Apple intends to manage power distribution, charging cycles, and battery lifespan across two cells.
Given the foldable form factor and the need for robust battery life, a dual-battery system is a logical and necessary innovation for Apple's premium ultra model. The industry will be watching closely to see how the company integrates this technology into the iOS experience and whether it sets a new standard for future iPhones.
Source: 9to5Mac News