As it did with its smartphones, Xiaomi is also moving upmarket in the connected watch segment with its Watch S1. Steel case, sapphire crystal and leather strap make Xiaomi seem to enter the big league.
Overall convincing in the mid-range with its connected watch Mi Watch, Xiaomi is now aiming for the upper range with its Watch S1. Taking the technical base of the Mi Watch, including its heart rate and SpO2 sensors, the S1 is more luxurious with its sapphire crystal flush with its stainless steel case, which is attached to the wrist with a leather strap.
A large Amoled screen with permanent display, dual-band GPS, 5 ATM waterproofing, Bluetooth calls, wireless charging and a long 12-day battery life complete a technical sheet that allows the Watch S1 to compete with the best in its category. Xiaomi nevertheless remains faithful to its aggressive pricing policy.
Ergonomics and design
The Xiaomi Watch S1 can be seen as a sort of premium version of the Mi Watch, which was released a year ago. It corrects most of the flaws we found in the latter, primarily its overly plastic construction and the poor scratch resistance of its glass.
While the base of the S1 case remains in polymer, the entire upper part, including the bezel, is now in stainless steel with a glossy finish on top and brushed edges. A design of the most beautiful effect which immediately confers a luxurious aspect to the watch.
The scratch-resistant sapphire crystal fits perfectly into the case thanks to its beveled edges. It protects a large, well-defined 1.43-inch Amoled panel (466 x 466 px, or 326 dpi) whose near-perfect blacks blend in with the 3mm borders (4mm including the thickness of the case).
The 46.5 mm wide watch is still suitable for fairly wide wrists, as the strap is not designed for wrists that are too thin anyway (adjustable length from 157 to 241 mm). It's a pity that Xiaomi does not offer a smaller version of its Watch S1.
Xiaomi is no longer content to provide a fluorinated rubber strap with its watch, it equips its Watch S1 by default with a leather strap, black or brown depending on the version. The leather strap looks a bit dry at first, but it becomes more supple with use and is quite elegant. For sports activities, especially swimming (5 ATM water resistance, i.e. static resistance to a depth of 50 m) or simply for a question of personal preference, it is possible to replace it with a rubber strap provided. The spring bar attachment system makes it quick and easy to change.
With its 12 mm thickness (10.9 mm if we do not take into account the sensors' island that is slightly embedded in the wrist to ensure more reliable measurements), the Watch S1 is comfortable to wear. The strap offers a good fit and a good support on the wrist. However, the S1 is somewhat overweight due to its use of glass and steel, weighing 64g on our scale.
The interface of the Xiaomi Watch S1 is mainly based on its touch screen. The top button on the right-hand side is used to return to the main dial or to display the list of applications, while the one underneath is used by default (its action can be changed in the Mi Fitness application) to open the activities menu to quickly start one of the 117 sports activities that the watch offers.
The touch operation is otherwise very intuitive and responsive. A downward swipe brings up the latest notifications, while an upward swipe opens the shortcuts pane (do not disturb, silent, alarm, settings...). A sideways swipe causes a scrolling of the different widgets, organized differently than on the Mi Watch, because they are now grouped by default. This avoids having to scroll through many screens, as the details remain accessible with a simple tap on the desired widget. This way, we can quickly check our heart rate, the duration of last night's sleep, the activity gauges (number of steps, calories burned and number of times up during the day), the weather or the audio player. The organization of widgets can be changed in the smartphone application.
A good point is that an ambient light sensor allows the watch to automatically vary the light intensity of its screen. It's a pity that it doesn't go down more than that for night use though. Fortunately, an automatic "do not disturb" mode takes care of turning off the screen during the night and disabling the automatic lighting by wrist movement.
As far as dials are concerned, there are many choices, from the classic digital hands with integrated complications, to animated dials and more sporty dials. Many other dials are available for download. It's a pity, however, that the definition of some dials is not higher, because even the default dial displayed when the watch is first turned on doesn't particularly honor the almost infinite contrast and good display resolution of the Watch S1's Amoled panel (visible aliasing on the hands, limited contrast).
Equipped with a speaker and a microphone, the Xiaomi Watch S1 can be used to take phone calls via Bluetooth. The sound seems somewhat muffled and the speaker quickly becomes saturated, but the conversation remains intelligible and the watch manages to eliminate some of the ambient noise to maintain good voice intelligibility.
Recently updated, Xiaomi's application is now common to most of the manufacturer's watches and bracelets. Renamed Mi Fitness, it does not change fundamentally, keeping its division into four tabs. The first is the home screen, where you can find the main information in the form of widgets corresponding to those displayed by the watch, but with more details: heart rate of the day and the last weeks and months, sleep tracking, number of steps, stress level, blood oxygen, etc.
The second tab allows you to launch running, walking, outdoor cycling or treadmill activities from the application. We would have preferred it to be dedicated to the activities performed with the watch, in particular to obtain more details and a real sports follow-up which is missing from this Watch S1. You can of course find the details of the activities performed directly from the main screen, but it lacks an analysis part that would be more interesting than raw data.
A third tab contains all the watch settings, from the choice of dial to the selection of activity times, including the choice of widgets to be displayed. The fourth tab is reserved for user and application settings. The operation of Mi Fitness remains simple and is suitable for users who are not looking for exhaustive data on all their activities.
Uses and accuracy
With no less than 117 indoor and outdoor sports activities, the Xiaomi Watch S1 is very comprehensive. You can generally find the activity that suits you and specific parameters are associated with each of them. The watch manages split exercises and you can set alerts to know when to change your pace, for example.
Equipped with a dual-band GPS chip, the Watch S1 offers satisfactory geolocation accuracy, despite some erraticities and a tendency to smooth out the routes on the map. It's a pity that the watch doesn't offer route tracking, however.
On the cardio side, the sensor does not seem to have changed compared to the Mi Watch. Unfortunately, it did not give us good results, including for endurance activities that usually do not pose too many problems for connected watches. The readings obtained with our Polar H10 chest belt - which we consider very reliable - during a rowing session correspond to a stable curve, while the curve retrieved via the Mi Fitness application shows a great irregularity in the measurements made by the watch, even after several minutes of exercise, the Watch S1 does not pick up the correct heart rate until the end of the activity.
With such a result, we expected the worst for a split activity. Here again, there are whole sections of measurements that do not correspond at all to those taken by our chest belt. The watch also clearly underestimates the heart rate, with a difference of over 55 beats per minute. This is unusable as it is, which is a pity, because we noticed during our test of the Mi Watch that it was able to follow the variations in heart rate. Note that the Watch S1 Active that we used at the same time on our other wrist did not do better on these exercises, generating different curves, but just as crazy.
Surprised by these results, we continued our investigations by doing a bike ride this time, with a relatively stable pace on the way out and much more variation on the way back. Unfortunately, the Watch S1 and the Watch S1 Active do not do any better on the outward journey, with curves that are far from the one obtained with the Polar H10. On the way back - with the watches tightened one more notch on the wrists to be sure of their good position - the Watch S1 Active produced a completely wrong curve, while to our great surprise, the Watch S1 gave its first good results, as we can see on the screenshot below.
Unfortunately, the results are too variable for us to recommend this watch to athletes who want to record their heart rate accurately. If possible, we will try to repeat the tests when the watch's firmware is updated, since it is possible that Xiaomi may correct the situation.
Xiaomi promises up to 12 days of autonomy in normal use for its Watch S1, thanks to a 470 mAh battery and good energy management. A duration that can actually be reached with the default settings, if you do not practice too many outdoor activities that require the use of GPS.
With sleep and stress monitoring during the day, the autonomy is logically reduced, but still allows to exceed without problem the week of use. The activation of the permanent display (always on) proves to be the most demanding, causing the autonomy to drop much faster. The watch is nevertheless able to last several days in intensive use, thus surpassing many connected watches that sometimes struggle to last more than 2 days.
Charging is done by induction with a magnetic base that is simply connected to a USB charger smartphone. It takes about 2 hours for a full charge.
Elegant and very autonomous, the Xiaomi Watch S1 is much more attractive than the previous Mi Watch and seduces with its finishes and display. Easy to use and equipped with most of the functions you'd expect from a connected watch, it does suffer from an inaccurate heart rate monitor that will put off experienced athletes hoping for a fairly detailed analysis of their performance. Nevertheless, it is a homogeneous and pleasant to wear connected watch, capable of meeting most traditional needs.