The iFixit teardown of the Apple Watch Series 3 found the guts of the device are mostly the same as the Apple Watch Series 2, minus the new LTE components that give the new device its cellular capabilities. The 1.07 Whr battery only provides a 4 percent increase over the previous model — by comparisson the Apple Watch Series 2 got a 32 percent improvement in battery capacity over the original Apple Watch.
Apple promoted the barometric pressure sensor as a new addition during its Keynote, and while iFixit found it in a new place in this model, the site discovered one in the Apple Watch Series 2 as well. The lack of changes to the new device has led to speculation that Apple had been planning to make the Apple Watch Series 2 a cellular device but didn’t quite make it in time — as was reported at the time — but it’s also possible that making the Series 2 GPS-compatible laid the groundwork for what would come after.
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