Maybe you installed the wrong size transformer for the thermostat...might not be providing enough of the power requirement and its drawing power from the batteries?
What is the voltage rating of your transformer? I think you need a 24 volt transformer, similar to the 'ritetemp' 24v as sold on EBay....do a search for 'transformer for wireless thermostat'....I'll bet that's your issue.
What is the voltage rating of your transformer? I think you need a 24 volt transformer, similar to the 'ritetemp' 24v as sold on EBay....do a search for 'transformer for wireless thermostat'....I'll bet that's your issue.