Thermostat displays B7 and indicates that the battery level is critically low (for battery‑powered models).

Safety first: Only handle batteries with dry hands and dispose of old batteries properly.

• Replace batteries: Open the thermostat battery compartment and replace all batteries with new, high‑quality alkaline cells of the specified type (e.g. AA or AAA). Do not mix old and new batteries.
• Inspect contacts: Check for corrosion on the battery contacts. If present, gently clean with a cotton swab and a small amount of isopropyl alcohol, then allow to dry.
• Reduce backlight time: In settings, reduce display backlight duration and brightness if possible to extend battery life.
• Check wireless signal: Poor signal can increase power use. Improve Wi‑Fi or gateway proximity if battery life is very short.