Ref: https://www.facebook.com/groups/homeassistantgroupefrance/posts/1341826740040898/

[mathieucarbou]

Liberty_HA/sensors.yaml

Lines 539 to 545 in fb7ab38

	- platform: template
	sensors:
	hue_motion_sensor_hall_battery_level:
	friendly_name: "Hue Motion Sensor Hall Battery Level"
	value_template: '{{state_attr("binary_sensor.capteur_couloir_motion", "battery_level")}}'
	icon_template: '{%- if state_attr("binary_sensor.capteur_couloir_motion", "battery_level") <= 5 %}mdi:battery-outline{%- elif state_attr("binary_sensor.capteur_couloir_motion", "battery_level") >= 95 %}mdi:battery{% else %}mdi:battery-{{(state_attr("binary_sensor.capteur_couloir_motion", "battery_level")|float / 10)|round*10}}{%- endif %}'
	unit_of_measurement: '%'

template:
  # https://www.home-assistant.io/integrations/sensor/
  - sensor:
      - name: Hue Motion Sensor Hall Battery Level
        state_class: measurement
        device_class: battery
        unit_of_measurement: "%"
        state: '{{state_attr("binary_sensor.capteur_couloir_motion", "battery_level")}}'

homeassistant:
  customize:
    sensor. hue_motion_sensor_hall_battery_level:
      templates:
        icon: >
          if state_attr("binary_sensor.capteur_couloir_motion", "battery_level") <= 5
              return 'mdi:battery-outline'
          if state_attr("binary_sensor.capteur_couloir_motion", "battery_level") >= 95
              return 'mdi:battery'
          return 'mdi:battery-' + state_attr("binary_sensor.capteur_couloir_motion", "battery_level")|float / 10)|round*10}}
        icon_color: >
          [...]

(not tested)

Ref: https://www.home-assistant.io/integrations/template/

Template declaration and UI / icons are separated. You can have everything in 1 file if you use packages