After the teardown of the iPhone XS and iPhone XS Max that reveled several details about the smartphones, iFixit has completed teardown of Apple Watch Series 4 44mm model with LTE (A2008). This reveals a slightly bigger battery compared to the Watch Series 3, hidden barometric sensor, all-new optical sensor, surrounded by a new ring-shaped electrical sensor.
The reveals 1.113 Wh / 291.8 mAh (A2059) battery compared to 1.07 Wh / 279 mAh battery on the Watch Series 3 (38 mm), but it is 17% less than 1.34 Wh in the 42 mm Watch Series 3. The barometric sensor has been relocated to the speaker grille. Taptic engine is thinner and longer than the one in the Series 3. The new speaker which is 50% louder has a gasket for ingress protection.
The Apple-designed S4 system-in-package has Avago AFEM-8087 front-end module and it has ST Microelectronics ST33G1M2 32-bit MCU with ARM SecurCore SC300—the same eSIM as the Apple Watch Series 3, iPhone XS and the iPhone XS Max.
iFixit gives it 6/10 repairability rating same as the Watch Series 3, saying that the Series 4 feels much more thoughtfully laid out, but the incredibly tiny tri-point screws are a repair hindrance, and the component flex cables that are mounted directly to the S4 package needs skilled micro soldering to replace, and the S4 system that is encased in solid block of resin makes most board-level repairs impossible.