Garmin Fenix 3 - Garmin: Replacing the Battery in your Heart Rate Monitor ( HRM) The CR2032 batteries in your HRM-Run, HRM-Swim or HRM-Tri straps will last approximately 18 months, depending on use.
Garmin HRM-Dual battery replacement – Chris Worfolk's Blog
How To Change The Battery On A Garmin Heart Rate Sensor - YouTube
Amazon.com: Garmin 010-12955-00 HRM-PRO, Premium Heart Rate Strap, Real-Time Heart Rate Data and Running Dynamics : Sports & Outdoors
HRM-Pro Plus Owners Manual - Replacing the Heart Rate Monitor Battery