How to get 120 hours of battery life on the OnePlus Watch 3

Ben Schoon | Feb 18 2025 - 10:30 am PT

The OnePlus Watch 3 is the best Wear OS smartwatch for battery life, but how can you actually get the claimed 120 hours of battery? Here’s how it breaks down.

Battery life is a struggle for most modern smartwatches because we’re asking more from these wrist computers than ever before. Between apps, fitness tracking, and so much more, the battery size can only stretch so far. There are two key things that the OnePlus Watch 3 does to fix that, however.

OnePlus Watch 3 launches with five-day battery life, health updates, Wear OS 5 for $329

Firstly, the OnePlus Watch 3 has a massive battery by smartwatch standards. The 631mAh battery inside uses “NanoStack” silicon battery tech which improves the capacity greatly without taking up additional space. The Watch 3 is barely bigger than its predecessor, but has a battery over 25% larger.

Beyond that, OnePlus is leveraging a dual-architecture system to intelligently switch between Wear OS, the high-power platform, and a custom RTOS, the low-power platform. These two are used for different tasks, with the RTOS handling things like the watch face and basic notifications off of a low-power BES2800 chipset, while Wear OS is ready for full apps and various other tasks that require additional power from the Qualcomm Snapdragon W5+ chipset. The transition between the two is surprisingly seamless, too.

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The mix of how you use those two platforms is the main way battery life will vary. For instance, using a non-official watch face will have an immediate battery impact, as only the watch faces provided by OnePlus run fully on the RTOS, where others will need Wear OS. Generally speaking, you’ll drop from a 120-hour estimate to around 72 hours just by changing this one aspect.

OnePlus breaks down the 120-hour battery of Watch 3 with the following tasks/conditions for its “Smart” battery mode:

Using an official watch face, AOD off, default health monitoring.
Bluetooth connection – 14.2 hours/day
WiFi connection standby – 1 hour/day
Sleep monitoring – 6.5 hours/day
Raise wrist to light up screen – 220 times/day
Receive 130 messages/day
Screen operation (various applications) – 20min/day
Incoming call reminder 5s – 6 times/day
Bluetooth call – 5mins/day
Sync data between phone and watch – 500/day
Bluetooth + headset for music (Spotify) – 15mins/day
Outdoor running w/GPS 30mins/day
Alarm 3 times/day

If you change things up to use a non-official watch face, you can also extend some of those stats such as notifications received and still squeeze out 72 hours of battery life. OnePlus uses the following conditions to determine that time estimate:

Third-party watch face (Dual Engine Architecture is off), AOD is turned on, default
health monitoring.
Bluetooth connection + AOD standby – 12.2 hours/day
Wifi connection + AOD standby 2 hours/day
Sleep monitoring – 6.5 hours/day
Raise wrist to light up the screen 300 times/day
Receive 180 messages/day
Screen operation (using various applications) 30min/day
Incoming call reminder 5s/6 times/day
Bluetooth call 5mins/day
Google Maps linked navigation 15 minutes/day
Synchronize data with mobile phone and watch 500s/day
Bluetooth headset connection to listen to music (Spotify) – 30mins/day
Outdoor running 30mins/day
Alarm 3 times/day

Battery life is already very good, but there’s also a 16-day claim for “Power Saver Mode.” OnePlus says you can hit that figure using the following model:

All-day Bluetooth connection
90 minutes of outdoor exercise/week
Raise wrist to wake screen – 180 times/day
180 messages/day
5 incoming calls/day
5 minutes/day of Bluetooth calls
3 alarms/day
Sleep detection – 6h/day

For sake of comparison, Google similarly broke down its 24-hour battery estimate for the Pixel Watch 3 which includes more notifications, AOD turned on, and significantly longer Google Maps usage.

The OnePlus Watch 3 is available for pre-order now and shipping in late February.