The best foldable phones come with some compromises, and the iPhone Duo is no exception to that. You only have two main cameras, the screen is shorter than you’d find on other iPhones and the battery is noticeably smaller than the one in the iPhone 18 Pro Max — just to name a few.
But when it comes to battery, size only matters so much. There are a bunch of different factors that impact how long a device can last on a single charge, which is why testing is so important.
We have done our testing with the iPhone Duo, using a custom battery life test designed to mimic ordinary daily use. And the results are fairly impressive, even if they aren’t as impressive as they were on iPhone 18 Pro Max.
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iPhone Duo Battery Life Results
| Row 0 – Cell 0 |
Battery Life (Hrs:Mins) |
Battery Size (mAh) |
|
iPhone Duo |
13:20 |
4,883 |
|
Samsung Galaxy Z Fold 8 |
10:06 (New test) |
4,800 |
|
Samsung Galaxy Z Fold 8 Ultra |
14:33 |
5,000 |
|
Motorola Razr Fold |
14:44 |
6,000 |
|
Google Pixel 11 Pro Fold |
12:31 |
4,806 |
|
iPhone 18 Pro Max |
17:31 (New Test) |
5,567 |
We tested the battery life of the iPhone Duo, iPhone 18 Pro Max and Samsung Galaxy Z Fold 8 simultaneously, with all three phones situated side-by-side. The results of this test found that the iPhone Duo lasted 13 hours and 20 minutes, and unsurprisingly the iPhone 18 Pro Max lasted 17 hours and 31 minutes. The difference isn’t that surprising, since the 18 Pro Max has an extra 684 mAh of battery capacity.
How the Duo compares to the Z Fold 8 is rather interesting, considering the difference in battery size is a mere 83 mAh. According to this test the Duo lasted more than three hours longer than the Z Fold 8, which just goes to show how much of a difference energy efficiency and reduced power consumption can make.
I should also caveat this by pointing out that our original battery life test for the Galaxy Z Fold 8 review saw the phone last 12 hours and 19 minutes. The discrepancy is down to the fact that the Fold is now a little older, and the variables of the test environment may be having an impact. However, it’s worth noting that the original battery life result is still almost an hour less battery life than the Duo.
As for the Samsung Galaxy Z Fold 8 Ultra, the extra 117 mAh of capacity pushes the battery life a little bit further with an extra hour and 13 minutes of battery life. Though this is the original result, and that figure did not come from a brand new battery life test.
The iPhone Duo also exceeds the battery life of the Pixel 11 Pro Fold, which died 49 minutes faster than Apple’s foldable. Considering the minor difference between the two battery sizes, and Pixel phones’ reputation for less-then-stellar battery life, that’s not a huge surprise. Likewise it’s not shocking that the 6,000 mAh Motorola Razr Fold lasted 14 hours and 44 minutes, considering how much more battery capacity it has.
iPhone Duo charging speed
| Row 0 – Cell 0 |
15 minutes |
30 minutes |
Charge Speed |
|
iPhone Duo |
42% |
66% |
60W |
|
Samsung Galaxy Z Fold 8 |
43% |
70% |
45W |
|
Samsung Galaxy Z Fold 8 Ultra |
49% |
76% |
45W |
|
Motorola Razr Fold |
42% |
75% |
80W |
|
Google Pixel 11 Pro Fold |
29% |
56% |
30W |
|
iPhone 18 Pro Max |
44% |
77% |
60W |
The iPhone Duo is meant to offer 60W charging, the same as the iPhone 18 Pro Max, but that doesn’t mean it charges at the same rate. In fact, despite having a larger battery, the 18 Pro Max draws in power much more quickly. After 15 minutes it was at 44%, compared to the Duo’s 42%, and after half an hour of charging the foldable had 11% less power than its non-folding sibling.
It’s a similar situation with the iPhone Z Fold 8 and Z Fold 8 Ultra, both of which are limited to 45W charging speeds. The Ultra hit 49% after 15 minutes, while the smaller battery in the Fold 8 reached 43%. After half an hour the two phones held a respective 76% and 70% charge. Meanwhile the Razr Fold, which supports up to 80W wired charging, had 75% of its power restored after a 30 minute recharge.
Unsurprisingly the Pixel 11 Pro Fold comes out much worse for wear in this test as well. It only managed to recoup 29% charge in 15 minutes and 56% after half an hour — a problem exacerbated by its limited 30W charging speeds.
How we test phone battery life
The key thing we should mention about battery testing the iPhone Duo was that our typical test had to be redesigned to fill the entire screen. Otherwise it wouldn’t have been a very fair test. The test itself involved continually surfing the web over a 5G connection, with the screen brightness set to a consistent 150 nits.
In the case of foldable phones, this test is always performed on the larger folding screen.
All phones we test go through this process, though so far only three have gone through this newly optimized testing regiment. They are the iPhone Duo, Samsung Galaxy Z Fold 8 and the iPhone 18 Pro Max. In this instance all three phones were tested in the same room, with the tests running simultaneously.
Bottom line
Overall the iPhone Duo’s battery life is rather middling compared to its rivals, but that’s not to say that it’s bad. The battery isn’t good enough to land a place on our best phone battery life list, but it should be enough to get through a typical day without having to carry a charger with you.
Those hoping to prioritize strong battery life above all else will want to stick with the non-folding iPhone 18 Pro Max. It’s a sad fact that foldables are just a little too power hungry to outpace their single-screen counterparts in the battery department. But as far as foldables go you could do a lot worse than the iPhone Duo.
Though, admittedly, two Android rivals offer over an hour extra battery life as well. Likewise many of them charge faster than Apple’s phone, even if regaining 42% in 15 minutes isn’t a particularly slow recharge speed. That should, at the very least, get you through a good part of your day before the usual low battery anxieties start knocking at your door.
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