OPPO Watch S2 revealed early with FatMax, ECG and 10-day battery

OPPO hasn’t officially launched the Watch S2 yet, but someone forgot to tell the internet. With just a few days to go, the new smartwatch has already appeared in extensive hands-on coverage, leaving surprisingly little for OPPO to reveal on September 22.

The China launch is scheduled for 7 PM local time alongside the Find X10 series, and OPPO itself is already showing the Watch S2 in its event material. More importantly, several Chinese publications have now spent enough time with the watch to give us a pretty complete picture of what is coming.

It looks familiar, but gets even lighter

OPPO has not messed around much with the basic formula. The Watch S2 sticks with the circular design of the original OPPO Watch S, including the crown and secondary button on the right side of the case.

Thickness remains at just 8.9mm, while weight has dropped slightly from around 35g to 34.4g without the strap. There are three colours this time around, Mountain Shadow Grey, Vibrant Orange and Misty Pink, along with a new segmented sports strap designed to flex more easily around the wrist.

Up front is a 1.46-inch AMOLED display with a 464 x 464 resolution and 317 PPI. Typical brightness is quoted at 600 nits, rising to 1,500 nits outdoors and as high as 3,000 nits in supported workout modes. The watch also carries 5ATM water resistance and supports wet-touch operation.

So visually this is very much Watch S territory. The bigger changes are happening underneath.

FatMax is the big new feature

The main addition is something OPPO calls FatMax. Rather than simply showing calories burned or placing users into generic heart rate zones, the system attempts to identify the intensity at which an individual is oxidising fat at the highest rate.

The calculation uses personal information such as height, weight, age, sex and existing exercise data to establish a target heart rate range. OPPO says the estimate becomes more personalised as the watch gathers more data over time. During a workout, it can provide visual, vibration and audio guidance to help keep the user within that range.

The clever bit is how OPPO presents the result. The Watch S2 estimates fat burned in grams during the session and provides a post-workout FatMax analysis rather than simply showing total energy expenditure. More than 16 workout types are said to support the feature, including running, cycling and treadmill incline sessions.

There is also a dedicated incline treadmill mode that records gradient, distance and accumulated climbing. Workout information can be mirrored to a phone or tablet, which means heart rate and other metrics can remain visible without repeatedly checking the wrist.

Strength training has received attention too. The watch can reportedly recognise more than 65 strength exercises, count repetitions automatically and provide rest reminders. Afterwards, it can generate training-volume information and a muscle activation heatmap.

Health tracking goes beyond the basics

The sensor package includes ECG, optical heart rate, SpO2 and wrist temperature monitoring. OPPO claims its updated optical sensor provides 75% better resistance to interference and quotes 98.8% heart rate accuracy during exercise, although those are company figures rather than independent testing.

ECG readings take around 30 seconds using the large electrode built into the side button. Chinese pre-release material says the software can identify sinus rhythm and flag possible atrial fibrillation, while sleep tracking includes sleep apnea risk assessment.

There is also a 60-second health check that brings several measurements together and provides longer-term trend information. Both the ECG software and sleep apnea risk assessment are reported to have Chinese Class II medical device registrations.

Another addition is workout readiness. The AI exercise coach can use sleep, HRV and recent training load to assess the user’s current state and suggest appropriate exercise. That puts the Watch S2 closer to the recovery and readiness features that are becoming standard across higher-end sports watches.

It is worth noting that OPPO has not carried over every health experiment from its premium watches. The company’s Watch X3 sits much higher up the range, while the Watch S2 appears more focused on fitness, everyday health monitoring and keeping the hardware thin.

Dual-band GPS and two phones at once

Sports tracking covers more than 100 modes, with dual-frequency L1+L5 satellite positioning onboard. That part is not actually new for the S series, but keeping dual-band positioning in such a slim watch is still worth noting.

The more unusual feature is dual-phone connectivity. Watch S2 can reportedly remain paired with two phones simultaneously, including Android plus Android and Android plus iPhone combinations. Notifications, incoming calls and messages from the secondary device can then appear on the watch as well.

OPPO has also expanded its remote camera controls. Users can preview the phone camera on the watch, adjust zoom, trigger a timer and take photos remotely. A pinch gesture can be used as the shutter, with pre-release material quoting control distances of up to 10 metres outdoors and five metres indoors.

Fluid Cloud 3.0 handles glanceable information from more than 40 supported app scenarios, including food deliveries, transport, navigation, tickets and sports scores. As with several of the smarter Watch S2 features, much of this functionality is designed around OPPO’s Chinese software ecosystem.

As far as Battery capacity, this comes in is 330mAh. OPPO rates the Watch S2 for around seven days under normal use, up to 10 days in lighter usage and roughly four days with the always-on display enabled. A full charge takes about 90 minutes.

Price, release date

The main missing piece now is price. OPPO will formally unveil the Watch S2 in China on September 22, but given how much information is already circulating, there may not be many hardware surprises left for the stage. We are also yet to learn when/if the device will be coming to international markets.

Sources: Oppo, Sohu, ZOL.