One of mine had a battery and the other didn’t. These are truly “open-box”. They take the weirdest battery size I have ever seen. CR2477. It’s like a button cell battery that you would find in your cars’ remote, just way thicker. Had I known this, I would have gone with the Honeywell. At least that one is compatible with the Ring app and uses batteries that you can find just about anywhere.
You bought this online and you are complaining about going to a store to buy batteries? Why not just buy some on Woot’s parent company… you know… Amazon (https://www.amazon.com/Panasonic-CR2477-Litium-Coin-Battery/dp/B002LHE678)? You still don’t have to leave the house. Even if you do have to buy a new battery, it’s still cheaper than hopping in the car and getting these at Home Depot (https://www.homedepot.com/p/ecobee-SmartSensor-2-Pack-EB-RSHM2PK-01/309221992).