Apple says its Apple Watch Series 3 offers "all-day battery life" with 18 hours of usage, but in some cases, the LTE model's battery will drain more quickly.

The 18-hour usage metric includes 90 time checks, 90 notifications, 45 minutes of app use, and a 30-minute workout with music playback, and on the LTE model, it includes 4 hours of LTE connection and 14 hours of connection to iPhone via Bluetooth.

When talking on the Apple Watch or working out, though, battery life is shorter when using an LTE connection.

The Series 3 Apple Watch offers 1 hour of battery life when talking to someone on the phone over LTE, or three hours when connected to the iPhone.

For audio playback when connected to the iPhone, the Apple Watch battery will last for up to 10 hours, which is an improvement over the Series 2 (6.5 hours). Apple does not mention how long the battery will last when listening to music over an LTE connection, but the Apple Watch Series 3 will support streaming from Apple Music without an iPhone.

When it comes to workouts, the Apple Watch battery will last for up to 10 hours during an indoor workout with an iPhone nearby, but that number drops for an outdoor workout sans iPhone. With just GPS activated, the battery in the Series 3 Apple Watch will last for five hours (the same battery life as the Series 2 with GPS on), and when connected to LTE and GPS the battery will last for four hours during an outdoor workout.

According to Apple, the Apple Watch Series 3 will charge to 80 percent in one and a half hours and 100 percent in two hours using the included Apple Watch Magnetic Charging Cable. These charging numbers are identical to the Apple Watch Series 2.

Apple's Series 3 Apple Watch models will be available for pre-order on September 15, with the device launching on September 22. Pricing starts at $329 for non-LTE models, and $399 for LTE models.