Changing the batteries on a Honeywell thermostat system is quite simple. It only requires knowing how to locate the batteries and access them. All Honeywell thermostats that have batteries store the batteries in the control panel. Locate the batteries by removing the battery compartment tray or cover or by removing the unit's faceplate.. This video shows how to change the batteries in a Honeywell thermostat and which batteries they take.
Step 5. Install the batteries - Reconnect the wall plate to the wall mount on Honeywell Home models and reinstall the battery compartment on FocusPRO™ units. Step 6. Check the installation - Turn the HVAC system back on using the thermostat switch. If the display lights up, the batteries are installed correctly.. Remember to match the polarity of the batteries with the + / - marks inside the battery compartment. 3. Complete the battery replacement process by securely reinstalling the thermostat onto the wall mount plate by pushing the thermostat back into place until you hear a click.