Apple Watch battery life: how many hours does it last?

Apple Watch battery size and mAh explained

Apple Watch battery life how many hours does it last

No one wants to have to charge another gadget every day, but the limited Apple Watch battery life - like nearly all smartwatch batteries - requires daily charging.

That's led to me be constantly asked, "Well, how long does that thing last?" whenever I explain the Apple Watch to people. The answer is more complicated than any one number.

The official Apple Watch battery life specs are listed as both "all day" and "up to 18 hours," according to Apple. Note: there are still 24 hours in a day.

Yes, that "all day" claim technically syncs up with a normal sleep schedule and it takes only two and half hours to fully recharge. But Apple's methodology behind these numbers and how they compare to the best smartwatches deserves a deeper dive.

How is Apple Watch's battery life calculated?

Apple Watch battery life hours

Apple claims that its iPhone-compatible smartwatch achieved all-day battery life of 18 hours during tests based on a pre-production Apple Watch and pre-production iOS software.

Its 18 hours of "mixed use" consisted of 90 time checks, 90 notifications, 45 minutes of app use and a 30-minute workout with music playback via Bluetooth.

Check the time or light up the screen fewer times, and Apple Watch's battery could beat these estimates.

Get a deluge of notifications, and it may die on your commute home from work.

More Apple Watch battery life tests

More granular tests by Apple yielded different results. A "watch test" netted 48 hours from five time checks every hour, with Apple noting that each screen-lighting timecheck lasted four seconds.

Apple Watch battery life tests hours
The Apple Watch battery life varies greatly based on use

The most power-draining battery test was a "talk time test" using the Apple Watch phone app. It lasted three hours in this Dick Tracy-esque mode that still required a connected iPhone.

Apple's "workout test" and "audio playback test" each resulted in 6.5 hours of battery life. The company said the heart rate sensor was on during the workout session.

Apple Watch Power Reserve mode

What happens when the Apple Watch battery is about to die? Instead of becoming a wearable sundial, it can still tell the time in what the company calls a "Power Reserve" mode.

Apple Watch power reserve mode 72 hours
You get 72 hours with the watch face in Power Reserve Mode

Like today's best smartphones, this special battery-saving mode turns off app functionality in favor of giving users the ability to check time on the smartwatch for up to 72 hours.

This little known three-day extension is based on four time checks per hour, again lasting four seconds each time.

Apple Watch 42mm size battery life

The Apple Watch battery size is 205mAh for the 38mm case. The 42mm case battery size is unknown, at least until someone brave (or who can afford the Apple Watch price twice-over) does a second teardown.

Until then, we know that the battery is the same in all cases, from the entry-level aluminum Sport to the pricey stainless steel Watch to the ridiculously expensive gold Watch Edition.

Apple Watch 42mm vs 38mm battery life size
The larger 42mm Apple Watch on the left has a slightly bigger battery

However, the larger 42m Apple Watch size has a bigger battery than the smaller 38mm version. That fact and the larger touchscreen area make this the better choice for most people.

Apple Watch charging time

As fast as the Apple Watch battery drains, it recharges even quicker using Apple's MagSafe inductive charger, which is included in the box.

Recharging the smartwatch to 80% takes 1.5 hours, according to Apple's official tests, and a 100% full charge takes 2.5 hours.

That's about the same time as other smartwatches I've tested, which of course you won't really notice at night, unless this thing constantly dies on your before the day is through.

Is the Apple Watch battery replaceable?

Apple Watch is unlike a smartphone that's destined to be upgraded every year or two, so it's important to be able to replace the battery eventually.

Apple watch recharge charge time hours lifespan years
Apple Watch recharges in 2.5 hours and lasts 3 years

While this is no easy task compared to a normal watch, the sealed battery can be replaced by Apple for an unspecified amount.

The good news is that this manufacturer-replaceable battery will reportedly last three years, at which time you'll need to seek the assistance of Apple Geniuses.

Let's see how it does versus its chief rivals, Android Wear and Pebble watches.

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