Although Apple has said that the Apple Watch will need to be charged nightly, the company has not disclosed any details on how long the wearable’s battery will last. For the first time, people with knowledge of the Apple Watch’s development have provided us with the specific performance targets Apple wants to achieve for the Apple Watch battery, but the actual numbers may fall short of those targets.
According to our sources, Apple opted to use a relatively powerful processor and high-quality screen for the Apple Watch, both of which contribute to significant power drain. Running a stripped-down version of iOS codenamed SkiHill, the Apple S1 chip inside the Apple Watch is surprisingly close in performance to the version of Apple’s A5 processor found inside the current-generation iPod touch, while the Retina-class color display is capable of updating at a fluid 60 frames per second.
Apple initially wanted the Apple Watch battery to provide roughly one full day of usage, mixing a comparatively small amount of active use with a larger amount of passive use. As of 2014, Apple wanted the Watch to provide roughly 2.5 to 4 hours of active application use versus 19 hours of combined active/passive use, 3 days of pure standby time, or 4 days if left in a sleeping mode. Sources, however, say that Apple will only likely achieve approximately 2-3 days in either the standby or low-power modes…