Apple’s new smartphones take advantage of the company’s first in-house designed power management chip, but the bigger news is that iPhone XS seems to have borrowed some of the coolest terraced battery designs we first saw in 2015’s 12-inch Retina MacBook.

iPhone XS/Max batteries

Here are the hard numbers:

  • iPhone XS Max: 3,174 mAh
  • iPhone XS: 2,658 mAh
  • iPhone X: 2,716 mAh
  • iPhone XR: 2,942 mAh
  • iPhone 8 Plus: 2,675 mAh

iPhone XS Max, of course, has the biggest battery of any iPhone model to date.

The iPhone XR battery capacity came from Chinese site MyDrivers ahead of the keynote so don’t take it for granted before the XR hits next month and iFixit does its ritual teardown dance.

iPhone XS introduces contoured battery design

With form-factor devices like smartphones, one is always wise to take advantage of all the technological solutions at one’s disposal to maximize every millimeter of space and deliver long battery life. Since the 12-inch MacBook’s terraced battery, Apple’s increasingly sought to take advantage of every bit of space in the iPhone chassis.

For the new iPhone XS, they developed a contoured battery shaped as the letter “L”. It’s the first time any iPhone has implemented a contoured battery design. The single-celled battery also marks the first gapless battery design in any iPhone model to date.

The new design approach removes material from the electrode layers before they are stacked.

“Notching” the battery

Because the L-shaped cell has six sides rather than four like a rectangle, each corner is sealed to prevent undue stress from thermal expansion. To reduce the stress on the corners even more, Apple has effectively “notched” the internal corner of the battery, as seen above.

“This dramatic shift opens up a lot of design possibilities, but the large notch is responsible for the decrease in capacity relative to iPhone X,” iFixit observed. “It will be interesting to see how this new battery performs as it ages,” they added.

At 2,659 mAh, the XS battery is slightly downgraded from last year’s 2,716 mAh iPhone X battery. However, the slight capacity decrease is offset by this “wild new battery configuration” where this L-shaped recess is filled with a single part rather than a pair of connected batteries.

2015 MacBook debuts terraced batteries

This is hardly Apple’s first foray into weirdly-shaped batteries.

In 2015, Apple released the single-port 12-inch MacBook with the Retina display. The notebook debuted a terraced battery design, layered in individual sheets to fit every millimeter of space in the curved enclosure. The patented solution increased total battery capacity by a whopping 35 percent than would be possible with traditional battery cells.

Terraced battery takes advantage of every bit of space in the MacBook chassis

Apple’s patents work around issues such as thermal expansion by using a terraced battery structure which uses variably-sized layers and precisely folding electrode sheets. These are cut into complex shapes to fit the notebook’s strict, precise contours.

And now they’re adapting this technology for iPhone.

iPhone XS Max battery

iPhone XS Max packs in a 12.08 Wh (3,179 mAh at 3.80 V) battery that also looks like the letter “L” but is a two-part solution so no single-cell here like on its smaller brother.

iFixit commented that XS’s contoured single-cell does a better job of utilizing space, but “packs less punch” because the iPhone XS battery is slightly smaller than iPhone X’s dual-cell module.

Contoured design is not used for the iPhone XS Max battery.

iPhone XS Max two-cell battery (left) and iPhone XS single-part cell (right)

“We suspect this marks the beginning of a new era in iPhone battery design—the carefully contoured single-cell concept is limited to the smaller iPhone XS for now, but we expect to see it again soon. iPhone XR, perhaps?,” iFixit speculates.

For those wondering, the iPhone XS and Max batteries are both in the ballpark of Samsung’s Galaxy S9 and S9+ batteries, but far smaller than that of the recently-released Galaxy Note 9.

Both new iPhones scored a solid 6 out of 10 on iFixit’s repairability scale, thanks in part to ease of display and battery replacements. The crackable back glass design, remains an expensive repair headache because the entire chassis must be replaced if the back glass cracks.

iPhone XS teardown images courtesy of iFixit