Apple Watch 4 teardown reveals a few new parts and redesigned interior

It made sense to peer into the iPhone XS first, but now we’ve gotten an inside look at the Apple Watch 4. An iFixit teardown has shown us that while there are only a couple new elements, Apple has shifted around the smartwatch’s internal parts to eke out a bit more sound and battery.

The biggest addition is the new pair of sensors, which operate as electrodes allowing the smartwatch to take ECGs. The first is a conspicuous gray ring on the bottom of the watch, while the other is within an updated digital crown, which the user squeezes with their other hand during a reading. The watch measures voltage between the two to take an ECG.

Photo credit: iFixit

Photo credit: iFixit

Apple has shifted around the internals of this year’s smartwatch, and we’re seeing benefits. Since the microphone has been moved closer to the digital crown, there’s more room for the speaker, which has been enlarged to produce 50% louder sound, Apple claims.

The new S4 chip includes an ST Microelectronics ST33G1M2 32-bit MCU, the eSim found in the Apple Watch 3 and now the iPhone XS. It’s the first time an eSim has been included in the company’s smartphone line after being tested in other Apple products. 

The battery capacity has been increased about 4% to 1.113 Wh (291.8 mAh at 3.81 V), up from 1.07 Whr (279 mAh at 3.82 V) in the Apple Watch 3. In our tests, we found the new smartwatch far exceeded Apple’s claim of an 18-hour battery life, which can stretch to two days if you use it lightly.

Insides aside, the Apple Watch 4’s external changes are noticeable, but only if you’ve been paying close attention to the smartwatch line over the years.

The Apple Watch 4 is actually slimmer than its predecessor by 0.7 mm. Interestingly, it’s not thinner than the original Apple Watch: The product line got thicker after adding GPS and water resistance with the Apple Watch 2, as The Verge pointed out.

The Series 4 watch again comes in two models, both in larger dimensions than the two for its predecessor -- 40mm and 44mm compared to 38mm and 44mm, which has increased the screen area by 30%. 

If you want to get technical, means this year’s bigger model manages 977 sq mm of surface area compared to 740 sq mm in the Apple Watch 3. The Series 4’s smaller 40mm version reaches 759 sq mm compared to 563 sq mm for its predecessor’s 38 mm version.

David Lumb

David is now a mobile reporter at Cnet. Formerly Mobile Editor, US for TechRadar, he covered phones, tablets, and wearables. He still thinks the iPhone 4 is the best-looking smartphone ever made. He's most interested in technology, gaming and culture – and where they overlap and change our lives. His current beat explores how our on-the-go existence is affected by new gadgets, carrier coverage expansions, and corporate strategy shifts.