What are the batteries for in a wired myson mprt room thermostat, I presumed if your stats are wired there is no need for batteries?

Martin Wright, November 2021

A very brief look at the wired version clearly shows the wired connection is for switch contacts that turn your heating on or off. There is no power feed as such to the device. The battery runs the temperature sensor, the microcontroller, display and a latching relay that controls the boiler.

Dfgxw, November 2021