Apple’s new iPhone Air is full of compromises, but surprisingly for such a thin device, the battery isn’t quite as bad as we’d feared. This could be down to a new kind of “remixed” battery chemistry which can more than double the number of possible recharge cycles. But it still doesn’t magically make a small battery able to power a phone for as long as a big battery.
The Air’s Embarrassing Secret
When Apple’s John Ternus explained the iPhone Air in its latest keynote video, he described it as a vague “amazing all-day battery life.” Only when he mentioned the new MagSafe battery pack did he switch to hours.
Even on the website, it seems like Apple goes out of its way not to share the mAh rating. Fortunately, the EU requires Apple and others to publish energy labels on store pages, and Mac Rumors’ Joe Rossignol dug out the numbers.
Let’s Physical
There’s a reason for Apple’s creative framing of the iPhone Air’s battery life: physics. You can’t just shrink a phone and hope to get the same battery life and performance you’d get from a bigger model. To be fair, it seems to have done a better job than we might have expected, but despite holding the battery life at similar levels to last year’s iPhone 16 Pro, a smaller battery is bad news for other reasons.
iPhone 17 3,692 mAh
iPhone Air 3,149 mAh
iPhone 17 Pro 4,252 mAh
iPhone 17 Pro Max 5,088 mAh
The relevant numbers here are for the Air and the 17 Pro, which are almost the same size in terms of screen area (6.5 inches for the 17 Pro, 6.7 for the Air), and use the same A19 Pro system on a chip (SoC). That’s roughly 25% less charge capacity.
Interestingly, Apple says that the iPhone Air can play video for up to 27 hours, vs the 17 Pro’s 33 hours, which is an 18% decrease. This suggests that video playback is heavily optimized, and we expect the difference under real-world usage to be quite a bit worse.
Wear and Tear
It’s all very well squeezing extra performance out of a battery by optimizing the hardware to use less power, but you still have a smaller battery. It’s just not going to last as long as a bigger battery, which means that you’ll be charging it a lot more often. I still use an iPhone 12 mini, with notoriously bad battery life, so I know all about that.
The problem is, a battery only has so many useful charge cycles in its life. After a certain number of cycles, its capacity will drop, and you’ll have to charge it even more often, which will reduce the capacity even more.
The best way to get a long life from a battery is to have a bigger one than you need, and only charge it to around 80% of its capacity. This can increase the overall useful lifetime of the battery significantly—up to 4x in fact. But with a battery running at its limits, like that in the iPhone Air, charging to 80% might mean the difference between lasting through the day, or having to top off the charge to get you over the line.
Apple knows this, which is why it has introduced a new MagSafe battery pack, which takes the claimed max video playback from 27 hours to 40. Of course, this means that you have a battery stuck to the back of your phone, and despite the promise in the keynote that you can still slip the package into a pocket, what’s the point? After all, the entire reason for buying the iPhone Air is that it’s slim and light. If you’re going to use the battery all the time then why not get the 17 Pro, which has better cameras too?
Plus, that MagSafe battery is itself inefficient. Any charger that transfers power through magnetic induction wastes around 25% of electricity as heat. On its blog, Anker, maker of batteries, cables, and other charging products, says that “The efficiency rate of inductive chargers usually falls between 70% and 80%.” This figure can climb nearer 90% with optimized practices, which includes lining things up with magnets like MagSafe.
Remixed Chemistry
A lithium battery typically lasts for around 400 charge cycles, which will get you through three to four years. Solutions to this include battery management systems that limit the total charge, and slow down charging when the battery is hot or nearly full, both of which can lead to irreversible degradation.
Another mitigation is to encase batteries in a metal shell. The shell contains outgassing, restricts swelling, and protects the battery cell from accidental damage. Combined with easy-to-release adhesives, these shells make batteries easier and safer to replace
But now a new battery chemistry tech means that the life of a lithium battery could be extended to 1,000 cycles, or more than double the current life, keeping phones running for a lot longer.
We might find this in the iPhone Air, and it would make its undersized battery a lot easier to live with.
Half a Foldable
If you look at the exploded x-ray-style animations in Apple’s keynote, you’ll notice something else about the inside of the iPhone Air. The computery parts are all up in that bulge at the top, which Apple calls a “plateau.” Not just the cameras, as we’re used to, but also the SoC and almost everything else.
That makes sense if you want a really thin phone. But it also makes sense if you want to make a foldable phone, which is just two thin phones with a hinge. All the computer guts can go in one little bump, and both sides can be filled with battery.
We still don’t escape physics though. That second half of the phone still has a screen that has to be powered, so the overall battery life is likely to be very similar to that of this year’s Air.
Repairability
We’re very interested to open up this new phone and dig in. Will it be easier to replace the battery now that there’s much less in the way? Perhaps the rear panel will be an easy removal allowing almost direct access to the battery. Or maybe the structural requirements of such a thin device—even with the stiff titanium frame—will mean that it’s glued tightly into place? But who are we kidding? Probably with a phone this thin we’ll still be going in via the screen.
We’ll know when we open it up, and we really, really hope that Apple has made at least some improvements here. If not, then the foldable iPhone is going to be twice as bad.
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