Battery life can vary based on brand, use, and other things however, a new CR 2032 battery should power your Kinsa QuickCare thermometer for approximately 2 years if used once every day, or roughly 600 temperature readings.
To extend battery life, try to have your phone nearby when taking readings. If your phone is far away, QuickCare will transmit readings until your phone is within range, using more energy. The closer your phone, the less energy your QuickCare will use!
QuickCare uses one replaceable CR 2032 battery. They're available at all pharmacies, most grocery stores, and online at Amazon.com, Target.com and Walmart.com.