Consider that missing link among the Apple Watch specs solved. It has a tiny 205mAh battery for the slightly smaller 38mm case size, according to the teardown experts at iFixit.
An Apple Watch runs out of juice, on average, after about 18 hours of normal use. It lasts anywhere from three hours if it's making a battery-taxing call, to 48 hours if it's performing simple time checks.
The 42mm Apple Watch has longer battery life, according to Apple, but it's likely to be marginally bigger in size. It takes 1.5 hours to recharge it to 80% and 2.5 hours to reach the full 100% again.
Battery specs: Apple Watch vs Android Wear
To put that 205mAh number into perspective, Android Wear's longest-lasting watch, the Sony Smartwatch 3, boasts a 420mAh battery with a day and a half of battery life. It leads our best smartwatches list.
What this means for Apple Watch
No Google watch beats Sony's smartwatch, though it's clear that every Android Wear watch has still fit in a larger battery than the "iWatch," which is a surprising considering the extreme Apple Watch price.
All of that said, how long a smartwatch lasts depends on other two factors. First, the more obvious how much the wearer uses the device, especially how often he or she lights up the screen.
Second, is the less obvious question of how demanding that software is. Android Wear, for example, is known to be fairly taxing compared to Samsung's lightweight Tizen operating system, which runs the company's longer-lasting Gear 2 and Gear 2 Neo watches.
Whether or not you get all 18 hours from this tiny Apple Watch battery may depend on how WatchKit apps are optimized on the wrist. It's really a balancing act between performance and battery life.
- More about the Apple Watch battery life