The folded iPhone Duo, Galaxy Z Fold 8 and Xiaomi 18 Fold standing side by side on a table
In a continuous Twitch-streaming battery test run by the tech channel Rozetked, Apple’s iPhone Duo lasted 9 hours 44 minutes, more than two hours longer than the Xiaomi 18 Fold (7 hours 36 minutes) and the Samsung Galaxy Z Fold 8 (7 hours 18 minutes). That result came despite the Xiaomi carrying a 6,000 mAh silicon-carbon battery, about 23% more capacity than the iPhone Duo’s 4,883 mAh. The test suggests that, at least under this kind of load, efficiency mattered more than raw battery capacity.
What you need to know
- Rozetked streamed the same Twitch broadcast on all three foldables at maximum brightness over LTE until each phone died.
- iPhone Duo (4,883 mAh) lasted 9 h 44 min, Xiaomi 18 Fold (6,000 mAh) 7 h 36 min, and Galaxy Z Fold 8 (4,800 mAh) 7 h 18 min.
- During the test, the Xiaomi reached about 40°C and appeared to throttle, while the iPhone Duo measured 34°C.
- The results use a custom method and cannot be compared with Rozetked’s earlier battery tests.
Why battery life is a particular challenge for foldables
Battery life is often an afterthought when choosing a foldable phone, but the source argues it deserves more attention. Two large displays, a thin body and a hinge in the middle leave little room for a battery, and manufacturers take different approaches: some focus on optimization, others on new battery chemistry and bigger capacity figures. On paper, the phone with the most milliamp-hours should last longest. This test did not end that way.
The usual test would not run on the iPhone Duo
The test was carried out by Rozetked, and the details are shown in the channel’s video. The channel normally tests phones by auto-scrolling through short videos, but that did not work on the Duo. According to the source, neither TikTok, YouTube nor third-party auto-scroll apps ran properly on the foldable iPhone, because many apps have not yet been adapted to its screen. A separate method had to be devised. The video’s author described it as the most difficult battery test in the channel’s history, taking around seven 10-hour runs before everything came together.
Xiaomi 18 Fold, iPhone Duo and Galaxy Z Fold 8 showing the same stream at the start of the test, with each phone’s screen and battery capacity listed underneath
How the phones were tested
In the end, all three phones played a Twitch stream. This creates a constant load on the display, the video decoder and the modem, with no pauses. The conditions were the same for every device:
- brightness set to maximum;
- an eSIM from the same mobile carrier and an LTE connection on all three phones;
- the same broadcast at the same quality.
The folded iPhone Duo in a hand, with a clock and sand-dune wallpaper on the outer screen
Important caveats
One detail put the iPhone at a disadvantage. The Duo’s maximum brightness is noticeably higher than its rivals’, and the Twitch app on it displays the picture with bars along the edges. The testers could not make the video fill the screen, even in a browser. So the Duo did not start under the most favorable conditions. Another important caveat: these results cannot be compared with Rozetked’s previous tests, because this test used its own method.
A 6,000 mAh battery did not decide the outcome
On paper, the matchup looked predictable. The Galaxy Z Fold 8 has a 4,800 mAh battery, and the iPhone Duo has slightly more at 4,883 mAh, split into two cells of 2,962 and 1,921 mAh. The favorite was the Xiaomi 18 Fold, with a 6,000 mAh silicon-carbon battery. The source describes this chemistry as a key advantage for Chinese manufacturers: its higher energy density allows more capacity to fit into the same body. The Xiaomi’s battery is 23% larger than the Duo’s.
A red Xiaomi 18 Fold standing half-open on a white table
The results
The source author added a column showing how many minutes each phone ran per 1,000 mAh of capacity, which makes efficiency easier to compare.
| Phone | Battery | Runtime | Minutes per 1,000 mAh |
|---|---|---|---|
| iPhone Duo | 4,883 mAh | 9 h 44 min | 120 |
| Xiaomi 18 Fold | 6,000 mAh | 7 h 36 min | 76 |
| Galaxy Z Fold 8 | 4,800 mAh | 7 h 18 min | 91 |
The Samsung gave out first, which the source calls a normal result for a foldable. The Xiaomi lasted only 18 minutes longer, an improvement of about 4%, even though its battery is 25% larger than the Samsung’s. In this test, the silicon-carbon battery translated into just 18 extra minutes.
The iPhone Duo shut down only after 9 hours 44 minutes: 2 hours 8 minutes longer than the Xiaomi and almost two and a half hours longer than the Samsung. Although the Xiaomi has 23% more battery capacity, the iPhone lasted 28% longer. Measured in minutes per 1,000 mAh, the iPhone managed 120 versus the Xiaomi’s 76, and the source argues that a bigger battery alone cannot close a gap of that size.
End of the test: all three phones have run out of battery, with the iPhone Duo shutting down last after 9 hours 44 minutes
The brightest phone ran the coolest
While the batteries drained, other details emerged. According to the source, the streams on the Xiaomi and Samsung regularly froze and at times fell more than 30 seconds behind the iPhone. The iPhone barely stuttered, even though it showed only two bars of signal while its rivals showed more.
An unfolded Galaxy Z Fold 8 held in a hand against a park background
The Xiaomi fared worse. It apparently began to throttle: the stream ran at 60 frames per second, but the on-screen frame rate at times visibly dropped to what looked like roughly 30 fps, and the picture stuttered. That frame-rate estimate was made by eye rather than measured. During these slowdowns, the testers measured the phones’ body temperatures:
- Xiaomi 18 Fold: about 40°C;
- Galaxy Z Fold 8: about 38°C;
- iPhone Duo: 34°C.
In other words, the brightest screen in the test belonged to the coolest-running phone. The source suggests that some of the Xiaomi’s extra capacity may simply have been lost as heat, although this is an interpretation rather than a measured finding. The test’s author had praised the Xiaomi in an earlier review and, after this experience, admitted it gave him something to think about. The test itself went noticeably more smoothly on the Duo, with no buffering or stuttering.
Apple’s battery claims appear to hold up
The source notes that the iPhone Duo has its share of quirks, but says battery life is not one of them. Apple promises up to 44 hours of video playback on the outer screen and up to 31 hours on the inner screen, and 37 and 26 hours respectively for streaming. For comparison, Apple rates the iPhone 18 Pro at 33 hours of streaming. That means the Duo should outlast the Pro when using its outer screen, but fall noticeably short on its inner one. According to the source, when use across both screens is combined and scaled against the iPhone 18 Pro’s results, the measured runtime lands close to Apple’s claims.
An unfolded iPhone Duo in a hand, with the home screen and app icons on the large display
How the Duo compares with regular iPhones
Rozetked also ran the Duo through its standard, more demanding battery test against regular iPhones. In that test, it lasted 7 hours 7 minutes. Its battery is 14% larger than the iPhone 18 Pro’s, yet it ran 12% shorter. That may sound underwhelming, but the Duo has two screens, one of them measuring 7.6 inches. For a foldable, the source calls this an excellent result.
Battery life chart: iPhone Duo 9 h 44 min, Xiaomi 18 Fold 7 h 36 min, Galaxy Z Fold 8 7 h 18 min
Should battery life decide your foldable purchase?
The source author’s verdict is that buyers who prioritize battery life can consider the iPhone Duo, provided they have no other objections to it. The author says it comfortably lasts a day of active use and that, among foldable rivals, it is currently ahead on battery life. That conclusion rests on these tests: a streaming comparison under a custom method and one standard test against regular iPhones.
The phone’s other issues have not gone away, however. According to the source, many apps are not yet adapted to its screen and bugs remain, so prospective buyers should look into those limitations before purchasing.
