Forerunner 920XT - Replacing the HRM-Swim Battery and the HRM-Tri Battery
thegearlife - Garmin HRM-tri In-Depth Review
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.