[Samsung Galaxy Watch] chaim32:
screen dominates battery drainage

Like many others, I skipped previous generations of smart watches due to battery concerns. My first smart watch was a Vector Luna, which used a e-paper display for 30 days of battery life on a single charge. That is hard to beat, but technology marches on.

The Galaxy Watch has an OLED display. One pays for beauty, and that includes more frequent charging.

Everything else being equal (e.g. GPS and WiFi off, no LTE, no Bixby, BT and notifications on, etc.), in my experience the main determinant of battery drainage is simply the amount of time that the screen is on.

The Galaxy watch has four screen modes:

ON, with a brightness based on your default settings and a time-out of typically 15 seconds, or a few seconds if a gesture turned it on

ON with "auto" brightness override (the same time-out period, but brighter, to overcome sunlight, for instance)

AOD, which is pretty dim (well readable in-doors, but hard to see in bright sunlight). the brightness setting has no effect on AOD.

OFF

The following values are for the the 46-mm watch:

With the screen OFF, and an occasional ON to look at the time or fool around with other apps, the battery drains at a little over 1% per hour. At night, since you don't get notifications, and you are not peeking at your watch, this goes down maybe to 0.5% per hour or so. If you check the time frequently, it will be a tad more than 1% per hour.

With a (dimmed) AOD screen, you will be discharging at about 2-2.5% per hour, probably depending somewhat on the watch-face design.

With the screen ON, particularly at high brightness levels, you are draining the battery a lot faster. You can see the battery drain a few percentages within several minutes of playing with the watch, changing faces or using applications that animate, check the internet for information, etc.

Do the math. With an 8-hour "sleep mode" and 16 hours of AOD, you are draining around 35-45% per day, enough for 2+ days, not quite 3 days. With the watch screen normally OFF, and only occasional peaks during the day, you will drain around 20-25%, or good for 4, almost 5 days.

This suggests two different battery-miser "strategies" for people who like to sleep with their watch strapped on:

AOD during the day, sleep & airplane mode at night, turn off gesture-activation! Peek at the watch any time during the day, and avoid turning the screen ON due to unintentional gestures. Use other features by turning the bezel or clicking a button. Charge every two-three days. This is my preferred mode.

No AOD. Use wrist gesture to turn on the display. Slightly further optimize battery by using sleep [ & airplane] mode at night. Charge every three-four days.

Note that the battery-level percentage indicator on the watch is a bit of a software guess, not precise science. And further remember that discharge is not precisely linear: a discharge from "100%" to 95% will take a longer time than a discharge from 25% to 20%, for the same workload.

Regarding your charging habits, as has been noted by many others: it is good practice to keep the battery level between 20-90, although we probably all like the satisfaction and sense of assurance of seeing the little green light and the magic 100% battery level indicator.

From what I can tell, charging time is about 40% per hour (using the travel adapter that came with the watch).

Please share your experience, particularly if it is different from mine. What do you see as other main contributions to battery usage?