I’ve spent a week with Apple Watch Ultra 4 – and it’s shaping up to be a serious endurance watch
Plus, a bigger battery inside
by https://www.techradar.com/author/jacob-krol · TechRadarFeatures By Jacob Krol Published 17 September 2026
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Alongside the unveiling of the iPhone Duo, AirPods 5, iPhone 18 Pro and 18 Pro Max, and the Apple Watch Series 12, the Cupertino giant also launched the Apple Watch Ultra 4. There’s no price increase, no major change to the design, and no change to the color options.
It’s a pretty similar upgrade to the Series 12, which you can read my preview of here — it gets the redesigned rear as part of the new health-sensing system, there’s a new S11 chip inside with a Secure Enclave and separate always-on processor, a new Readiness Score that looks set to take on Oura and Whoop, two new AI features will begin rolling out later this year, and it can deliver HRV (heart rate variability).
But one key change is a bigger battery: the Apple Watch Ultra 4 has a 5% larger battery than the Apple Watch Ultra 3, paired with more efficiencies to deliver Apple's promised runtimes. That means the Ultra 4 can truly go the extra mile, with a promised up to 50 hours in normal use, up to 84 hours in Low Power Mode, and up to 45 hours in Max Extended Workout Mode.
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Those are strong numbers, and thus far, it’s lasted in lockstep with the Ultra 3, offering more than a day of use and getting pretty close to a full two days. I’ll need more time with it before I can say whether that bigger battery and the efficiency gains translate into a meaningful real-world improvement, but so far, there’s plenty of endurance here.
There’s also a new Apple Watch Charger in the box. It looks the same as the previous one, but the cable has new tech that lets it charge even faster, with Apple promising up to 18 hours of battery life from a 15-minute charge. That’s mostly been the case in my testing so far, but I want to put it through some more charging cycles before I can say exactly how much of a difference it makes.
And just like with the Series 12, I’m holding off on a full verdict for now. The new Readiness Score is one of the biggest changes to the Apple Watch experience, and I want to give it enough time to build a picture of my data before I draw any conclusions. Apple says it generally takes seven nights of wear to calculate a score.
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The redesigned health-sensing system and more frequent heart-rate and HRV tracking are already interesting additions, particularly on a watch built around fitness and endurance. It’s paired with full activity tracking, dual-band GPS, hypertension notifications, blood oxygen tracking, and satellite connectivity. Being able to pull up real-time heart rate and have the watch sample this data more frequently should make the Ultra 4 even more useful for workouts, while HRV adds another metric that brings it closer to competing devices.
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