Q: how do I know when the battery is low on an iwatch?

Hi

The article below explains how to check the remaining battery charge on Apple Watch, including via:

- The Battery Glance and;

- A watch face complication that can be added to some watch faces (this shows the remaining battery charge whenever you view the watch face).

Check your battery and charge your Apple Watch - Apple Support

For details of how to add complications to watch faces, see: https://help.apple.com/watch/#/apdb0c5fb937