OPPO Unveils Watch S2 with FatMax Mode and 8.9 mm Case

OPPO has introduced the OPPO Watch S2, a mid-range smartwatch built around a thin, light case and workouts aimed at burning fat. Its headline addition is FatMax mode, which calculates a personal heart rate zone for the most efficient fat burning. The watch launched alongside the Find X10 smartphone series and the pricier Watch X3.

A personal fat-burning zone

FatMax, or maximal fat oxidation, refers to the exercise intensity at which the body burns the most fat. Heart rate zones are usually set with generic formulas, while OPPO's algorithm calculates them individually from the user's height, weight, age, sex and fitness level and refines them the longer the watch is worn. The mode works with more than 16 activity types.

During a workout, the watch uses sound, vibration and on-screen cues to help the wearer hold the target heart rate. Afterwards it shows an efficiency analysis, including how many grams of fat and carbohydrates were used. OPPO claims that training in this zone can burn twice as much fat in the same amount of time.

The treadmill incline mode has also been refined, logging distance, gradient and total elevation gain. Heart rate data can be mirrored in real time to a phone or tablet screen. In total the watch supports more than 100 sport modes, although open-water swimming is not among them.

Thin case and bright display

According to OPPO, its 8.9 mm thickness makes the Watch S2 the world's thinnest round smartwatch. It weighs about 34.4 g without a strap and between 58.7 and 60.6 g with one, depending on the colour. The case is stainless steel, while the back is made of glass-fibre reinforced plastic. A two-piece fluororubber strap is designed to sit closer to the wrist, which matters for overnight sleep tracking and heart rate accuracy.

The watch has a 1.46-inch AMOLED display with a 464×464 resolution. Typical brightness is 600 nits, rising automatically to 1,500 nits in direct sunlight and peaking at 3,000 nits in OPPO's own sport modes. It is rated 5ATM, IP69 and IP69K, meaning it withstands not only immersion but also high-pressure, high-temperature water jets.

Battery life and phone connectivity

The watch runs ColorOS Watch 17 on a BES2800BP chip. Its 339 mAh battery lasts up to 7 days in typical use and up to 10 days in the longest-lasting mode, or around 4 days with the always-on display enabled. A full charge via the magnetic connector takes about 90 minutes, and 10 minutes of charging provides a full day of use.

The Watch S2 works with phones running Android 10 or iOS 14 and later. OPPO highlights the ability to pair the watch with two phones at once and receive notifications from both, even when one runs Android and the other is an iPhone. Other features include a remote viewfinder for the phone camera with a gesture-controlled shutter, dual-frequency L1+L5 positioning, NFC and a built-in speaker. Wi-Fi and eSIM are not supported. The Chinese version also offers WeChat for the watch, Alipay and WeChat Pay payments, and Fluid Cloud notifications.

AI coach and health monitoring

Heart rate is measured with an 8-channel sensor and blood oxygen with a 16-channel sensor. The watch also has ECG electrodes, a wrist temperature sensor and fall detection with emergency calling. OPPO puts heart rate accuracy during exercise at 98.8%. A 60-second health check collects 13 metrics covering heart health, sleep and stress, and produces an overall AI-generated analysis.

The AI coach assesses workout readiness before training based on sleep quality, heart rate variability, stress levels and the past 7 days of activity. After a session, it advises whether the body needs recovery or can keep training.

An ECG reading takes 30 seconds and can flag signs of atrial fibrillation and premature beats. The ECG analysis software is registered in China as a Class II medical device.

Sleep apnea risk assessment analyses heart rate and breathing during sleep. This feature has also received Chinese Class II medical device registration.

Specifications

• Display: 1.46" AMOLED, 464×464, 317 ppi, 600 nits (typical), 1,500 nits (sunlight), up to 3,000 nits (peak)
• Processor: BES2800BP
• Case: stainless steel, glass-fibre reinforced plastic back
• Dimensions and weight: 45 × 45 × 8.9 mm, 34.4 g without strap
• Battery: 339 mAh, up to 7 days (typical), up to 10 days (maximum battery mode), up to 4 days with AOD; 2.5 W magnetic charging, about 90 minutes
• Sensors: accelerometer, gyroscope, magnetometer, barometer, optical heart rate, SpO2, ECG, wrist temperature, ambient light
• Positioning: dual-frequency L1+L5; GPS, BeiDou, Galileo, GLONASS, QZSS
• Connectivity: Bluetooth 5.2, NFC
• Protection: 5ATM, IP69, IP69K
• OS: ColorOS Watch 17
• Compatibility: Android 10 and later, iOS 14 and later

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