Here is how the battery and power saving work on the Slim X3 Bluetooth Backlit Keyboard.

Low-battery indicator: the power LED at the top right blinks red when the battery drops below 15 percent. Note that macOS does not show a battery percentage for our keyboards the way it does for an Apple Magic Keyboard, so it may display around 60 percent even when the keyboard is fully charged.

Battery life by brightness level, with the backlight on:

• Level 1: about 144 hours
• Level 2: about 81 hours
• Level 3: about 48 hours
• Level 4: about 32 hours
• Level 5: about 24 hours
• Level 6: about 19 hours
• Level 7: about 15 hours
• Level 8: about 13 hours
• Level 9: about 11 hours
• Level 10: about 10 hours

Power saving:

• The backlight dims to Level 1 after 1 minute of inactivity.
• The backlight turns off after 3 minutes.
• The keyboard enters sleep mode after 30 minutes.
• The backlight turns off automatically when the battery is below 15 percent.

Standby time is about 13 days, and working time is about 45 hours.