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Heart rate sensor active when using an external belt

I've recently replaced a Fenix 5 Plus with a Forerunner 245 (non-music)

I'm quite happy with the watch but battery life is very poor, only around 4 days between charges with about 5 to 6 hours of GPS. I've noticed that when using an external heart rate belt (I get the 'Ext. HR connected' so I know it's connected) the green LED are still flashing - with my old F5+ the built-in heart rate turned itself off. Since I spotted this I go into settings to disable the internal HR sensor during activities, but I feel I shouldn't have to do this. I think in part this is contributing to the power drain.

The watch is still on 5.0.0 firmware (I tend not to update because often firmware gets worse with more bugs introduced) so I'd prefer not to update if this is the normal behaviour with the 245. But if newer firmware solves it, I'll bite the bullet.

Thanks

0 8300582 over 4 years ago

Hi! I am using a Forerunner 245 (latest firmware) with a Garmin HRM-Dual strap.

Based on my observations, it works like this: although you will get the „External HR connected“ message after entering an activity screen (for example running), the watch will still use its internal OHR sensor right up to the moment when you actually start an activity. Once you start the activity (as in press the start button so that time / distance measuring begins) the external sensor is used. You can easily verify this by having a look at the bottom of your watch, you should see that the green lights are off once you start the activity. As soon as you end an activity by saving it, the watch will fall back to the OHR sensor again. This is automatic, you don't need to turn off the internal sensors in the settings.

In fact, I have found it is impossible to force the watch to use the external sensor outside an activtity, no matter what settings I use for the internal sensors.

When it comes to battery life, make sure to set your paired external sensor to „Off“ when you are not using it. Go to settings -> Sensors & Accessories and turn the sensor off. Otherwise, your watch will constantly be searching for the paired sensor. According to user reports it will cause slight additional battery drain that adds up over time and will be quite noticable.