iFixit teardown: 40mm Apple Watch Series 5 battery has a metal casing, instead of traditional foil pouch, which makes it physically stronger, and more compact
Context & Ripple Effects
iFixit has tracked the Apple Watch's internals since its 2015 teardown found a 205mAh cell and the S1 chip, and each generation's battery has been the story: Series 3 nudged capacity up to accommodate LTE, per an earlier teardown. The Series 5 finding — a rigid metal-cased battery replacing the traditional foil pouch — explains how Apple keeps fitting capacity into the same 40mm shell.
That packaging choice reads as groundwork for durability: Bloomberg reporting later pointed to a rugged Apple Watch with a shatter-resistant screen and non-aluminum metal case, and iFixit's own Series 6 teardown confirmed the payoff, with the 40mm model gaining 8.5% battery over the Series 5.
First-order effects
- Buyers of the 40mm Series 5 get a physically stronger, more compact battery in the same case size, trading away the flexible pouch format used in earlier generations.
Second-order effects
- A rigid metal casing constrains how repairers and third-party suppliers handle replacement cells, since pouch-style batteries are easier to source and shape-fit; iFixit's subsequent Series 6 capacity findings show Apple kept iterating within this tighter envelope rather than reverting.
Third-order effects
- If the pattern holds across Apple's lineup — the metal midframe iFixit later found in the iPhone 14 points the same direction — wearable and phone internals converge on rigid, durability-oriented structures, raising the bar for teardown-level repairability.
The trend: Apple's wearables are shifting from flexible-pack internals toward rigid, space-optimized construction that prioritizes durability and density over ease of repair.