Galaxy Z Fold 8 Ultra Battery Tests Show Capacity Is Not the Whole Story for iPhone Duo

In the tests, the Z Fold 8 Ultra's 5,000mAh Si-C cell outpaced last year's 4,400mAh lithium-polymer model in virtually all scenarios, according to Android Authority. The smaller Galaxy Z Fold 8, which has a 4,800mAh Si-C cell, was also competitive, likely because of its slightly smaller display. All three phones were close in 4K playback.

Other hardware changes offset some of those gains. Android Authority reported that the 200MP main camera hurt picture-shooting endurance, making the Z Fold 8 Ultra one of the worst performers in that metric by a notable margin. The phone retained reasonable 4K recording times. The outlet also said a faster processor may not have delivered the battery gains that might have been expected.

The benchmarks also compared the Samsung models with rivals. Motorola's Razr Fold has a 6,000mAh cell but could not break away from the group. Samsung's years of foldable performance optimization helped its more compact models score closely with, and sometimes outlast, the Razr. All of the tested phones outlasted the Google Pixel 11 Pro Fold and its 4,800mAh battery, according to Android Authority.

Android Authority said the results show foldable battery life is more about balance than brute capacity. The efficiency of the large internal display, processor optimizations, and camera hardware all affect runtime, and those factors can vary from generation to generation.

For Apple's iPhone Duo, the question is whether the company can make its first foldable last through a day. Apple has not given a capacity rating for the device. Android Authority noted vague figures such as 44 hours of video playback on the outer display, which it said is hardly a strong endorsement of longevity when the phone is used in its designed form factor. Reports have suggested a 5,400mAh capacity, which would be large for a first foldable, while others point to a more mainstream 4,800mAh cell. A teardown is expected to clarify the figure.

Samsung's adoption of silicon-carbon batteries remains significant, the outlet said, because a denser cell can give engineers more capacity without necessarily making a foldable thicker, heavier, or harder to design. But the tests suggest that adding hundreds of milliamp-hours does not guarantee hours of extra real-world endurance. Displays, chipsets, cameras, thermals, and software all play a role.

Apple may still have room to optimize the Duo. Android Authority said Apple does not need the biggest battery in a foldable to make a compelling first attempt. It needs to show that the battery can be used efficiently across two very different display configurations, and because Apple controls the processor, operating system, display behavior, and power management, it has opportunities to squeeze more runtime from the hardware. The outlet said the Duo will need to undergo the same battery tests before any conclusion can be drawn, and it concluded that the future of foldable battery life will not be won by capacity alone.