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I'm considering the purchase of a new GPS. The Garmin Edge 25 has most of the basic features I need. However, high accuracy is important to me as I do trail mapping for my local MTB club. I thought that getting a unit with GLONASS support would help improve accuracy, but I was concerned about runtime since the manual indicates it will reduce battery life.

What is the impact on battery life of enabling GLONASS support on the Garmin Edge 25?

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    Are you sure this question might not be better suited for something like: outdoors.stackexchange.com since it is clearly not about bicycles? – renesis Oct 26 '15 at 15:04
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    or even, ask Garmin directly, or visit the Garmin user forums? I must admit I've found their tech support a bit useless, but I've had some success asking about my 800 on their forums – PeteH Oct 26 '15 at 15:09
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    @renesis the Edge 25 is a bicycle-specific device. – Scott Hillson Oct 26 '15 at 17:55
  • I am unfamiliar with garmin devices, but I do run a super cheap/nasty cellphone with strava, and a gopro off a 10Ah USB battery. The cellphone normally gets ~4 hours and the gopro only got ~2 hours before they're flat, and with the USB battery I can run both for 12+ hours. I fit the phone and battery in a top-tube bag, and run a short USB cable to the gopro on the headtube. Works for me, and its much more flexible. Can the garmin run while being charged by USB? – Criggie Oct 26 '15 at 20:27
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    Can the garmin run while being charged by USB? - I don't know if It can be run while charging. However, it does require a special dock, so it likely can't be mounted and charging at the same time. – Benzo Oct 27 '15 at 16:45
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You're only going to experience roughly a 10%, (maybe 20% max) loss of battery life. Unless you're planning on frequent century or all-day rides, the difference is relatively negligible. The average use case, a commute to and from work, or the average 4 hour group ride, won't see any difference because the battery life will go from about 8 hours on a full charge to 7 hours.

If you do plan to take it on century rides or night rides, you might want to upgrade to a medium tier unit, 510/520/etc, as the medium sized units have nearly twice the battery life. Using the GPS+GLONASS mode doesn't have a significant effect on battery life at all in this case because we're looking at about 16 hours of battery life in GPS-only mode vs 15 hours of battery life with GLONASS. Unless you're living on the edge (no pun intended), the GLONASS mode isn't going to make it or break it.

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    For what it's worth, I always leave my Edge 520 in GPS+GLONASS mode and I've never used more than about 60% of the battery in a single day. – Scott Hillson Oct 26 '15 at 17:54
  • I have an Edge 510 which has GPS & Glonass. I would support the estimate of 20% reduction in battery life when Glonass is enabled. The accuracy and reliability is much better though, if you are in forested areas. – ObeyTheDiode May 10 '16 at 11:08
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I can share my experience with the unit. I love it for it's simplicity, but the battery life is becoming an issue after only a few months use. Yesterday we went out on a slow welcome back ride. 5 miles to the meetup point, 40 miles with a cake stop in the middle, then 5 miles home. I charged the unit overnight. Set out at 9:30 AM. Ran out of battery at 14:20 ish while we were chatting at the meetup point before heading home. I have GPS and GLONASS switched on. I'm planning longer rides this year, and hopefully me first hundred. I reckon I'll be averaging 13mph so I'll need the battery to last for 8 hours just with on the move time, without factoring in breaks, so I'm already looking at ways to extend the battery life, or upgrading within a year of purchase.

  • Welcome to Bicycles @Adrian. Thanks for answering one of our questions. As with all new members we recommend taking the tour to make best use of the site. – andy256 Jan 29 '17 at 13:19
  • Did you find a solution @Adrian? I'm having the same issues - it used to last 8 hours when I bought it, but now 6 months later it's only doing 5ish. – John Farrelly Apr 26 '17 at 20:29

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