Each Mila Finder comes with 2 CR2032 batteries. One is installed in your Finder and the other is an extra. The life of your Mila Finder's battery will vary depending on how much you use it. It is intended to last 3-6 months with regular use.  Note that CR2032 batteries are available in any place batteries are sold.Track your battery life within the app by selecting your connected Finder and viewing the battery icon in the top right corner of the screen.