At the moment, our M1 Mouse or Slim X3 Keyboard do not support the battery percentage feature on macOS similar to the Apple Magic Keyboard or Mouse.

Slim X3 Keyboard

Our Slim X3 keyboard actually notifies you it is low on battery with the power LED indicator found at the top right:

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The LED light will blink red when it has reached below 15% 

M1 Mouse

When your mouse or keyboard indicates that it is low on battery, we recommend charging your devices for 2-3 hours. 

For a more efficient charge, we recommend charging your devices through a power adapter that supports 18W and up. (not included)