This Home Assistant card shows the battery levels below a slider-adjustable percentage of all battery powered devices and sends a notification if one or more battery levels are 10% or less.
• Copy the YAML from binary_sensor.yaml and past it in your binary_sensor.yaml file.
• Copy the YAML from input_number_helpers.yaml and past it in your input_number_helpers.yaml file.
• Create a new empty automation, go in the YAML editor and past the YAML from the automations.yaml file.
• Change the entity of the service to the notify entity of your choice.
• Do a quick reload of the YAML configurations (Settings --> Restart Home Assistant --> Quick reload)
• Go to the dashboard of your choice, add a new manual card and past the YAML from card.yaml in the YAML editor.
• Save the card and you’re done.