Amazon.com: Garmin Monitor de frecuencia cardíaca HRM-Tri : Electrónica
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.
DIY guide to change battery : Garmin HRM Tri / Run / Swim Chest Strap - YouTube