I didn't realize it would still be in the warranty period. That's cool.

Even so, everything I've seen on the internet indicated that they would be swapping me a whole unit instead of sending me a battery to pop in. I was hoping to avoid that. Don't want to have to wire the old thermostat back in while I wait.

I had hoped that the battery would be something I could just easily source elsewhere.

But if it's under warranty and contacting them is the only way, then so be it. Thanks guys!