Undo the 3 screws(if present - using a PH1 screwdriver)
Pull the Thermostat from the wall.
Remove the battery clip on the reverse of the Thermostat.
Replace with 2 x AA Alkaline batteries.
DO NOT USE Zinc, Heavy Duty or Lithium Batteries.
How do I change the batteries?
How do change batteries on the Ignite Wireless Thermostat