comments:
Disclaimer, I don't own this product, but I've been eyeing it as it may be an option to throw under your watch when the battery starts to die and run with it for a bit and then tuck it away in your vest. https://a.co/d/02BCCnWL
I'd recommend testing with a variety of battery modes. You can test the watch while you're just going about your normal day to day, don't wait until you're 70 miles into a 100-mile race! I've got an old Fenix 6 Pro which gets about 40 hours of GPS runtime, many times that in "expedition mode" but that's less useful for constant use and step-by-step tracking. I've done marathons and adventure races and hikes that lasted for upwards of 30 hours and it was still fine. However, this time craters if I have a long sleep time on the auto-backlight and have multi-channel GPS recording at 1 second intervals. It's bad if I've got data fields that update every second or faster, especially bad if that screen is the map. I turn off Bluetooth (I don't need phone notifications mid-race) and of course turn off the WiFi (I'm not going to be at home). I don't think that anything is wrong with your watch, I think you may have used it in a way that demands more battery than you might have needed to use. Always-on display, auto-backlight, GPS mode, recording interval, and map display selections can result in very large changes to battery runtime. OTOH, a little battery pack like this: https://www.amazon.com/Charger-Garmin-Watch-Vivoactive-Forerunner/dp/B0F5L632HM is light and small, easily slips under the watch while I'm still wearing it, and brings it back from 20% to 80% charge mid-activity in about 45 minutes. It's good for about 3 charge cycles before the portable pack itself needs to be recharged.