The Clever Engineering Behind the New iPhone XS Battery

The overwhelming theme of iPhone XS evaluations? That Apple’s newest flagship smartphone does not differ a lot from final yr’s iPhone X. It appears and works about the identical, and nonetheless prices a bundle. But these similarities belie one essential distinction, an Apple innovation that hides beneath the floor: a battery with a impossible form.

The iPhone X, in addition to this yr’s iPhone XS Max, each depend on a dual-cell battery for energy. That is to say, they primarily use two rectangular lithium-ion models, positioned perpendicular to one another, to maintain these smartphones buzzing. Together, they kind the form of an L, snuggled up inside your cellphone.

There’s nothing notably thrilling about that. You’ll see some variation on it inside any smartphone that you just crack open as we speak. (Note: Please do not crack open your smartphone.) That’s simply how batteries for cellular gadgets, usually outsourced to third-party producers, get made. But not so within the iPhone XS, which as a current iFixit teardown exhibits, trades that dual-cell design for a single, steady L-shaped battery.

Taking the L

The apparent first query: why? The reply’s not as sophisticated because it may appear, though it comes with an asterisk. By having one huge battery as a substitute of two conjoined, you may ditch just a little little bit of packaging and remove the small hole between them, maximizing your capability. Picture two small prepare vehicles in a row. Next to these, put one other automotive that is so long as each small vehicles mixed. You can match extra into the one, since you’re eliminating two partitions and a few in-between area. The similar precept applies.

“They’re trying to miniaturize everything. You have to pack in as much energy density as you can into this batteries,” says Venkat Srinivasan, deputy director of the Joint Center for Energy Storage Research. “You’re constantly looking to ask yourself, can I decrease something that is not active in the battery? Can I make my current collectors thinner, can I make my separator thinner, and ultimately can I also make my packaging thinner?”

Every cellular firm pursues some model of this, generally too vigorously. (See Samsung’s exploding Galaxy Note 7 debacle.) Apple is the primary, although, to try to show the nook. And which may be the toughest trick to drag off but.

X-ray pictures of (from left) the iPhone X, iPhone XS, and iPhone XS Max.


You can probably credit score Apple’s capacity to make an L-shaped battery to a patent it filed again in 2012, detailing a brand new means match a lithium-ion battery’s guts into no matter form it desires. It first utilized these wiles in 2015, introducing a brand new “terraced” battery design in that yr’s new MacBook. In that occasion, it curved and stacked battery layers to suit each spare nook of the chassis.

The iPhone XS battery seems to take that very same breakthrough, and put it in a cellphone for the primary time. Theoretically, that maxes out the out there battery actual property. “The form factor on the outside is fixed by a design team, and the components take up what they take up. Everything else that is left, if you can pack it with the battery, that’s fantastic,” says Srinivasan. “With the L-shaped design, if you can minimize the packaging as much as you can, you get a little bit of a bump.”

But you additionally run into some probably scary chemistry. Which is the place that asterisk is available in.

Another Notch

The iPhone X famously popularized the “notch,” the front-facing black swoop that homes an array of digicam parts. The iPhone XS battery has a notch as effectively, a type of buffer space round that inside nook, designed to keep up the battery’s integrity because it angles round. In truth, the within of that L-shaped casing, the precise battery appears extra like a J.

The purpose: Batteries hate edges. And the extra of them you introduce, the extra potential issues you create.

“There are two problems to having an inward corner on a battery like this. It’s a very intricate, complex process to fold the layers of the battery in the first place,” says iFixit author Taylor Dixon. “But once the layers are folded, if you have an inward corner, that corner is harder to maintain a flat seal on, and that sealant is also more susceptible to breaking or corrosion during thermal expansion, when the battery’s hot.”

Enter the notch, which creates a sand trap-like buffer across the nook. Rather than a pointy inside angle, the iPhone XS battery really has a curve, which ought to assist its long-term integrity, and maintain it out of Note 7 territory. Dixon says notch additionally leaves sufficient room for Apple to place a correct seal on the battery, with out protruding past the confines of the L-shaped packaging.

“They’re trying to miniaturize everything. You have to pack in as much energy density as you can into this batteries.”

Venkat Srinivasan, JCESR

The upshot of the notch, although, seems to be that Apple has really given up, not gained, capability. The iPhone XS battery weighs in at 2,659mAh; final yr’s iPhone X edges it out at 2,716mAh. It’s potential that the general footprint of the XS battery is smaller than that of the X, to make means for different parts; the newer mannequin has extra RAM and a much bigger digicam sensor. But Dixon believes they’re comparable, and that the notch offsets the features made by switching from dual-cell to single. That may additionally clarify why the XS Max skipped out on the transition this yr. Apple didn’t reply to requests for remark.

Those trade-offs do not make the breakthrough any much less thrilling, although, particularly given what it portends. “I definitely know down the road this could enable bigger batteries in smaller devices, because they’re living out the dream of filling out the whole chassis with the battery,” says Dixon.

Which is about all that Apple or any firm can do, at the least till the following breakthrough battery materials comes alongside. Which may very well be some time.

“I’m a battery scientist, I’m always looking to discover new materials. And that’s hard, it’s really hard to do that,” says Srinivasan. “In the meantime, companies are also trying to say, while we wait for these battery materials to get better, can you find a way to squeeze more into whatever space we have? You can see how these designs come about. Here’s a little bit more you can get.”

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