When Apples first foray into the world of wearables was announced, the company noted that its Apple Watch would need to be charged nightly, but didnt disclose quite how long the devices battery would last.

The reason behind that reticence may now be clear, with reports suggesting that the Apple Watchs active battery life will be only two and a half to four hours. According to 9to5Mac, the relatively powerful processor and high-quality screen included in the Apple Watch are both a significant drain on the power, leaving it with a battery life that will barely get users through a busy morning.

Apple has been stress-testing the battery with pre-bundled and third-party apps, with heavy application use draining the battery within 2.5 hours, while heavy use of less intensive apps lasts around four hours. Even simply leaving the clock-face display on, so that the time is always available, empties the battery within three hours.

Combining active and passive use extends the batterys life span up to 19 hours, while leaving the wearable in standby mode gives it around three days of power, or four if left in sleep mode.

Of course, very few users are likely to spend long periods of time using the Apple Watch intensively, meaning the 19 hour mix of active and passive use will be closer to what most consumers experience, but this hasnt stopped the battery life being a considerable source of concern for Apple in the build-up to the watchs launch.