Wiser Room Thermostat shows E15 and the app reports an internal battery temperature or safety error.

Safety: If batteries are hot, swollen, or leaking, remove them carefully and dispose of them safely. Do not reuse damaged batteries.

• Stabilise temperature: Bring the thermostat to a normal room temperature environment and allow it to stabilise for 30 minutes.
• Fit new batteries: Install fresh alkaline batteries of the correct type, ensuring correct polarity.
• Inspect for damage: Check the battery compartment for signs of overheating or melting. If present, discontinue use and replace the thermostat.

If E15 persists with new batteries at normal room temperature, the internal monitoring circuit is faulty. Replace the thermostat.