Wiser Room Thermostat shows E05 and the app reports a power or battery issue; device frequently disconnects.

Safety: The thermostat is battery powered. Avoid mixing old and new batteries.

• Replace batteries: Fit a full set of new, high-quality alkaline batteries of the specified size. Do not use rechargeable NiMH cells unless explicitly supported.
• Inspect contacts: Check for white or green corrosion on the battery terminals. If present, gently clean with a dry cloth or pencil eraser. If heavily corroded, the thermostat may need replacement.
• Check orientation: Ensure batteries are inserted with correct polarity as marked in the compartment.
• Reboot and test: After battery replacement, wait for the thermostat to restart and reconnect to the Heat HubR. Confirm in the app that the battery level is normal.

If E05 continues with known-good batteries and clean contacts, the internal power circuitry is likely faulty and the thermostat should be replaced.