Me: "I didn't know it used batteries. Or how to get at them."
Wednesday: Me: *tries to pry open the thermostat, unsuccessfully* "I should look for the directions."
Thursday: Me: *looks at the thermostat for a model number. It doesn't have one*
Friday: Me: "Well, I'm renting a car today anyway, I can get whatever batteries it takes when I go for groceries."
Saturday morning: Thermostat: *display is dead*
Me: "I guess I should figure this out now." *does Google search for the brand name of White-Rodgers, which is the thermostat's only identifying mark*.
30 seconds later: Me: *removes faceplate, puts in fresh AA batteries*
That was ... unexpectedly easy.
Also, I can't believe that my thermostat ran for 12 years on two AA batteries. o.O