Apple Watch Series 8 and Ultra battery size discovered

These are the specs Apple hasn’t shared…

Apple Watch Ultra
(Image credit: Apple)

Apple likes to talk about battery life in hours rather than capacity, measured in milliamperes. As a result, the latest Watch Series 8 has a claimed life of 18 hours, just like its predecessor, and the new Watch Ultra manages a claimed 36 hours.

But what are the actual numbers? We’re glad you asked, because this is something certification agencies are able to reveal, and this time its China’s 3C agency, reported by GSMArena, that has come up with the goods.

According to the agency – and in keeping with common sense – the smallest battery is fitted to the smallest model of Apple Watch. Specifically, the new Watch SE has a battery capacity of 245 mAh in the 40mm model and 296 may in the 44mm version.

Next comes the Watch Series 8, which has a pair of slightly larger case options than the SE, at 41mm and 45mm, and these have battery capacities of 282 mAh and 308 mAh respectively. Interestingly, these do not vary between the Wi-Fi and LTE models of Apple Watch, despite the latter likely being more power hungry than its non-4G sibling.

These stats are actually down slightly on the Series 8’s year-old predecessor, the Series 7, which had a 309 mAh battery in the 41mm model

Lastly, the new Apple Watch Ultra, with its larger case, has the biggest battery capacity ever fixed to an Apple wearable, at 542 mAh. This makes it significantly larger than its stablemates – and it’s no surprise, given the claimed battery life being three times that of the Watch Series 8.

Apple says a new low-power mode, coming to the new generation of smartwatches later this year, can significantly boost battery life by scaling back and switching off some features.

The company claims the mode can increase the Series 8’s battery life from 18 to 36 hours, while the Watch Ultra’s life jumps from 36 to 60 hours – good for what Apple calls a “multi-day adventure” that includes 15 hours of exercise 35 minutes of app use, 15 hours of sleep tracking, three minutes of voice calls and over 600 time checks.

Alistair Charlton

Alistair is a freelance automotive and technology journalist. He has bylines on esteemed sites such as the BBC, Forbes, TechRadar, and of best of all, T3, where he covers topics ranging from classic cars and men's lifestyle, to smart home technology, phones, electric cars, autonomy, Swiss watches, and much more besides. He is an experienced journalist, writing news, features, interviews and product reviews. If that didn't make him busy enough, he is also the co-host of the AutoChat podcast.