iPhone XS Battery Has Apple's Second Notch

Last year’s release of the iPhone X saw Apple follow the trend of notched smartphone displays. This year the iPhone XS has a secretive second notch designed into its handsets to improve performance.

The second notch is inside the battery of the new iPhone XS (but curiously not the iPhone XS Max). Although ‘L-shaped’ on the outside, last year’s iPhone X battery was in fact two cells wired together. That’s a sensible decision when building up power cells - once you start adding in corners you have to take extra care over expansion at the edges of the cells during the charging and discharging phases. A direct ‘L-shape’ features six edges, and that causes all sorts of issues.

Apple’s solution is to make a battery that could easily be mistaken for a french curve ruler, which also has a circular notch at the crook of the L to help overcome the physical issues. The new design has come to light in iFixit’s teardown of the new iOS-powered smartphones:

The challenge with any lithium-polymer battery cell is that each corner needs to be sealed to prevent undue stress from thermal expansion—and since the battery of the XS has 6 sides vs. the traditional 4, those extra corners can be tricky. To reduce the stress on the corners, Apple notched the internal corner of the battery (as described in this 2016 patent). This dramatic shift opens up a lot of design possibilities, but the large notch is responsible for the decrease in capacity relative to the X. Only time will tell how this new cell performs with age.

The practical upshot is that Apple can build the iPhone XS with one battery cell and I presume there will be a positive impact on the bill of materials because of that. But it also reduces the capacity of the battery from the iPhone X’s 2716 mAh to 2658 mAh.

Now that the iPhone XS is freely available, expect real world battery life tests to be coming in over the next two weeks to add some context to Apple’s “thirty minutes more battery life” claim.

Now read more about the iPhone XS and its failure to innovate…