Edit the watch face, go to Customize, then Data, and cycle through the available options. There's one which is just a battery icon with the percentage remaining and another that includes a battery icon with the other status icons.
Edit: You can also always see the current charge percentage by long pressing the Menu button, it's displayed at the top of the menu.
5yrs later now 2022 thank you for your information. I lost my settings in rebooting my watch and lost the battery settings, thank you for your note being here