If you're a fan of smartwatches, you'll know that they're feature-rich, but every new generation of features comes at a cost. While our insatiable desire for our devices to do more shows no slowing, battery technology isn’t evolving at the same rate, and battery is one of the biggest concerns when picking a reliable smartwatch.
Unlike a phone, which can be designed a hair thicker to accommodate a bigger battery but hide it well, a smartwatch needs to be designed as a watch first, technology second. This doesn't bode well for smartwatch makers, and while devices such as the Garmin Venu 3 and Withings Scanwatch 2 achieve multi-day battery life, they offer a more limited feature set than the big three smartwatches from your phone maker: Apple Watch Ultra 2, Galaxy Watch 6 Classic and Pixel Watch 2.
So, which of these devices offers the best battery life and charging? Does all-day battery life really mean all day? Is the Apple Watch Ultra 2 battery that much better to justify its almost double price tag over the competition? Let's find out!
The idea of charging a smartwatch every night is inherently flawed. Rather than drain to empty and then full, all batteries are designed to work best between 20% and 80% charge. As a result, five 10-minute charges are better than a single 50-minute charge, and each watchmaker includes some form of fast “top-up” charging.
To find out how good this charging is, I measured the time taken to charge to full and the impact of a 15-minute charge. Note that the Galaxy Watch 6 Classic comes in two sizes, each of which has a different sized display and battery. The 43mm Watch 6 Classic has a 300 mAh cell; the larger 47mm model comes with 425 mAh. My testing was conducted with the larger model.
Apple Watch Ultra 2
Galaxy Watch 6 Classic (47mm)
Pixel Watch 2
Capacity
~564 mAh
~425 mAh
~306 mAh
Charge to full
93 minutes
82 minutes
78 minutes
15-min charge (%)
13%
21%
22%
None of these watches are fast to charge to full, although you won’t have an issue if you charge it overnight. In the top-up charging, a 15-minute charge should give you a few hours of extra usage, but 30 minutes is the ideal charge time to achieve an extra half day of usage.
It’s one thing to top-up charge when you can, but what about when your smartwatch battery is almost depleted and you still need it? What if you woke up and forgot to charge overnight; will your smartwatch battery see it through the second day?
During my testing, my usage was average-to-low, including usage of notifications, alarms, and health features, but not including any workout tracking. Workout tracking and active usage of sensors will likely impact your battery life, although the actual impact will depend on your specific usage. The tests below can be considered best-case scenarios with moderate usage of the core features that each smartwatch offers.
For this test, I charged each watch to full, wore them all simultaneously (each connected to a different phone with similar apps and complications), and checked their battery percentage at various intervals over two days. This isn’t the most scientific of tests, thanks to a range of variables, but it does indicate the endurance and battery patterns for each of these smartwatches.
In this test, the Pixel Watch 2 and the 47mm Galaxy Watch 6 Classic showcase almost identical endurance and battery usage patterns. Samsung and Google both claim all-day battery life, and it’s clear from this testing that both devices generally deliver. However, should you forget to charge overnight, it’s highly unlikely that you’ll make it to the end of the day without needing a top-up charge.
The Apple Watch Ultra 2 is an entirely separate discussion. Apple claims up to 36 hours of battery life (or up to 72 hours with power-saving mode turned on), and in my testing the Apple Watch Ultra 2 easily exceeded this.
How accurate is the one-day testing I performed above? I conducted similar tests over several days to decipher this, using all three watches simultaneously and individually. I logged the various battery life percentages and paid close attention to each smartwatch's individual battery life characteristics.
Most of my tests found that all three smartwatches followed the same battery trends detailed in the graphs. My more extensive testing also allowed me to determine average battery life, with each smartwatch tested and logged seven times (including simultaneous and individual use).
Here’s the average battery life I achieved with each smartwatch:
Apple Watch Ultra 2
Galaxy Watch 6 Classic (47mm)
Pixel Watch 2
Capacity
~564 mAh
~425 mAh
~306 mAh
Average Battery Life
46 hours 22 minutes
35 hours 19 minutes
33 hours 18 minutes
What about the maximum battery life? With power saving mode turned on, the Apple Watch Ultra 2 achieved 76 hours of battery life, the Pixel Watch 2 achieved 47 hours, and the 47mm Galaxy Watch 6 Classic achieved 48 hours. Using smartwatches in these modes renders most of their smart features useless, so I don’t recommend it, but it will help extend your battery life to see it through to the end of the day.
While we've focused on the Galaxy Watch 6 Classic and Apple Watch Ultra 2 in this comparison, Samsung and Apple offer alternatives you might also consider. The Apple Watch Series 9 costs half the Apple Watch Ultra 2 price but features a battery almost half the size (308mAh vs 564mAh). In our brief testing with the Apple Watch Series 9, we found the battery lasts around 32 hours, guaranteeing a full day's usage even under heavy usage.
What about the watch size? Here's how the battery sizes compare based on model and size:
Galaxy Watch 6
Galaxy Watch 6
Galaxy Watch 6 Classic
Galaxy Watch 6 Classic
Size
40mm
44mm
43mm
47mm
Capacity
300mAh
425mAh
300mAh
425mAh
As I touched on above, testing for this piece was conducted using the larger 47mm Galaxy Watch 6 Classic. The smaller 43mm model, naturally, comes with a smaller battery. You may also consider the Galaxy Watch 6 instead of the Galaxy Watch 6 Classic featured here. Aside from different case sizes, the 40mm Watch 6 and the 43mm 6 Classic have identical specs; ditto for the larger 44mm Watch 6 and 47mm 6 Classic.
Both smaller Watch 6 versions feature the same 300mAh battery, whereas the larger ones are standardized at 425mAh. With this in mind, we'd expect a marked decrease in battery life (and faster overall charging speed) with the smaller watch sizes, but the exact impact is to be determined. Assuming all things remain equal other than battery capacity, we'd expect the smaller batteries to reduce battery life, but the smaller watch face should negate some of the loss.
The biggest surprise for me in doing this testing? Every OEM delivers on its promise of all-day battery life, and each watch actually lasts longer in normal use. This is the opposite of how each company sells its phones, but it makes logical sense for them to under-promise and over-deliver on their battery life claims. Granted, your battery life will almost certainly vary based on your usage.
What about the Apple Watch Ultra 2? Is the extra heft and battery life worth the extra cost? The answer is not really, but with the caveat that it doesn’t matter: the Apple Watch Ultra 2 offers the best battery life of any Apple Watch and is considerably better than the Apple Watch Series 9. If you’re locked into the Apple ecosystem, you’ll ultimately pick one of these two.
If you’re an Android user, the Pixel Watch 2 and Galaxy Watch 6 Classic offer near-identical battery life. If this is your main deciding factor, I would probably pick the Galaxy Watch 6 as I prefer Samsung’s approach to health. There are two styles to choose from, and I find the Galaxy Watch 6 Classic to offer better overall value for money. If you pick the Pixel Watch 2, though, you likely won’t be disappointed by its battery life.
Nirave is a creator, evangelist and founder of House of Tech, which is focused on the intersection of health and technology. Following a heart attack at the age of 33, he’s been focused on how we can use data to improve our health and ultimately live a long and more fruitful life. Follow him on Instagram, Threads, and YouTube for live updates on his Sleep and Health journeys. He can also be found at HoT.tech.
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