If your sensor has a regular AA/LR6 battery installed, these can be bought at most convenience store. We recommend changing these batteries while you are changing the batteries in your smoke detector (once a year). The batteries in these pictures are special batteries utilized in our stove guard sensors, which have a long lifetime (3.6V Lithium battery). Here you can order both wall-mounted and ceiling-mounted stove guards. The batteries are different, so make sure to order the correct one.