When Apple unveiled the Apple Watch Series 4 a few weeks ago, the company told the audience that the new smartwatch has the same battery life as its predecessor. Soon after Series 4 hit stores, a teardown revealed that the new Watch has a battery that’s roughly 4% bigger than before. That comparison, however, was flawed. The actual batteries inside the new Apple Watch models are smaller than the batteries Apple used for Series 3, which makes Apple’s battery life claims even more impressive.
iFixit compared the 44mm Series 4 battery to the 38mm Series 3 battery, MacRumors explains. However, information on Apple’s own Product Information Sheet reveals that both Series 4 models have batteries that are significantly smaller than their like-sized predecessors.
The 44mm Series 4 model has a 1.12 watt-hour battery, which is 16.5% smaller than the 1.35 watt-hour battery of the 42mm Series 3 watch. The 40mm Series 4 model has a 0.86 watt-hour battery, which is 19.7% smaller than the 1.07 watt-hour battery found inside the 38mm Series 3 model. When it comes to overall size in terms of dimensions, both the 44mm and 40mm Series 4 watches are taller and wider than their 42mm and 38mm Series 3 counterparts. But they’re also slightly slimmer.
Apple’s battery estimates for Series 4 models are up to 18 hours of use, matching Series 3 numbers — the detailed estimates are available at this link. Apple Watch Series 4 likely includes components that are more efficient, including the display and the new SiP, which explains why they’d last just as long in spite of packing smaller batteries.
Obviously, real-life mileage will vary, depending on how you use the Apple Watch S4. But the Watch should definitely have enough juice to last through the day.