Teardown of 40mm Apple Watch Series 5 uncovers new battery design

What you need to know

iFixit's teardown of the 40mm Apple Watch Series 5 reveals a new battery design.
Instead of a foil pouch, the battery is enclosed in a metal casing.
iFixit said the metal casing is more space efficient and makes the battery physically stronger.

Earlier this week, iFixit tore apart the 44mm Apple Watch Series 5, finding that the wearable is very similar to the now discontinued Series 4. You'd expect the same findings inside the 40mm Apple Watch Series 5, but that's not entirely the case.

iFixit looked inside the 40mm Apple Watch Series 5 and discovered a 10% larger battery along with a new battery design.

Instead of the usual dark-colored outer foil pouch surrounding the battery (which most lithium-ion batteries sport), we noticed a snazzy new metal casing, most likely aluminum. This is the first time we've seen this is an Apple product, and it might tell us something about the future of battery replacements.

According to iFixit, Apple appears to have implemented a battery design described in this patent. Essentially, Apple was able to cram more battery in the Apple Watch Series 5 thanks to a more space-efficient metal casing.

"The traditional foil pouches leave a larger seal than this new metal enclosure, meaning Apple can theoretically put previously-wasted space to good use," iFixit said.

Not only is the new metal casing more space-efficient, but iFixit said it makes the battery physically stronger.

"This is fantastic for repair purposes, since it's all too easy to puncture a lithium-ion battery during repairs," iFixit said.

Finally, iFixit said the new battery design could potentially make battery replacements much easier down the road, because it may allow the battery to be secured to the device with screws, rather than adhesive.