An Apple Watch takes a couple of hours for a full charge although there are a number of factors that can affect the charge time, including the exact Apple Watch model, the charger used, as well as various environmental factors. While the exact charge time will vary, most Apple Watches shouldn’t have any issues being fully topped up within a few hours.
Apple Watch comes with plenty of features and benefits that make the purchase worthwhile, but it is still a smartwatch, and battery life remains one of the major issues affecting this type of product. In general, smartwatches running on Android tend to offer long levels of daily usage with the built-in rechargeable lithium-ion battery on most Apple Watch models tending to max out at eighteen hours.
An Apple Watch is capable of receiving a full battery charge in 2.5 hours, according to Apple. However, this time-frame should only be considered a guide considering the exact time will vary to some degree. For reference, Apple’s official charge time is based on the company’s testing using an Apple Watch SE along with the Apple Watch Magnetic Charging Cable and the and Apple's 5W USB Power Adapter. Using any other cable or adapter can affect how long it takes to charge an Apple Watch.
Understanding Apple Watch Charging Speeds
It is worth being aware of just how an Apple Watch charges as this can help wearers to make the decision of how long they actually need to charge their smartwatch. For example, while it takes 2.5 hours to fully charge an Apple Watch, a significant portion of that time is just getting the battery level up from 80-percent to 100-percent. Essentially, Apple uses fast charging to charge the smartwatch up to 80-percent. At which point, the charging speed changes to a slower trickle charge for the remaining 20-percent. Apple employs this method in a bid to extend the overall lifetime of the battery.
Considering an Apple Watch only relies on fast charging for the first 80-percent, some Apple Watch owners may find that’s enough battery to get them through the day. If that is the case then the Apple Watch will only take 1.5 hours to reach the 80-percent charge level. In other words, if time is an issue, then Apple watch wearers can just charge the device for 1.5 hours to get a mostly full battery and, when time is less of a concern, leave the smartwatch on charge for 2.5 hours to fully recharge the battery.
Source: Apple