Pushing the envelope: Ultra-long time tests on Timex Run Trainer andFR910XT

Earlier last month someone on one of the various Internet Forums had asked how long the Garmin FR910XT and Timex Run Trainer would last if you turned off GPS, and instead let it just rely on ANT+ data (heart rate, speed, cadence, power, footpod).

Curious, I decided to set out and try it out.  It probably doesn’t surprise you to know that many of my posts here start off as questions or inquiries from you – be it here directly, or on forums and posts.  Despite a massive backlog/list of post ideas, I’m always looking for cool post ideas – and this was definitely one of them!

The first challenge was how was I going to do a workout that lasted at least 20+ hours (the known battery length of the GPS on for the FR910XT)?  Well, let me tell ya right up front, you won’t see me doing any of those crazy deca-Ironman races (10 times the length of an Ironman).  Thus, that ruled that out.  And even if I wanted to ‘just’ do two back to back Ironman’s…I’m reasonably certain that I’d probably just end up stopping at the first Dairy Queen I saw and ruining the whole test.

So, I was left to figure out a different way of getting 20+ continuous hours of ANT+ data.  And that brought me to the ANT+ Simulator.  The ANT+ simulator is used by companies developing and testing their ANT+ devices, to validate that the devices integrate properly within the ANT+ ecosystem.  It’s much easier than hiring a bunch of high schoolers to stand ready on treadmills that pedal or run on command.

Plus, it’s free.  So I grabbed it from the ANT+ site and went to town.  The tool allows me to create up to eight sensor types, each with different streaming data. I decided that cycling had the most ANT+ sensor types available for use during sport, so I went with that: Power, Speed/Cadence, and Heart Rate.  But since the Timex Run Trainer doesn’t support a cycling profile for ANT+ devices, I also added in the footpod too – which it does support.


I then configured the tool to provide a sweeping dataset, so it would be easy for me to glance over and validate it was still both transmitting data – and thus that the unit was receiving data.  This way it looked like the cyclists was constantly speeding up or slowing down, and the same for power and heart rate.


Then I got low-tech, I went and grabbed a simple kitchen timer.  Now this thing only goes to 24 hours, but after that it just resets itself.  Given I could at least remember the day I started, I was ready to go.


And off they went!

Now, this part isn’t terribly exciting.  They just sat there.  And the numbers changed.  And then they continued sitting there.  With both units the backlight was turned off, and the GPS also turned off.  Here’s what they looked like:



In the middle of this test, the Motoactv joined the fun for its initial battery life tests.  In fact, the ANT+ simulator would stay running for over a month straight, just being there for any tests I needed.  I had both running and cycling data streams being outputted constantly.


A few days later, the FR910XT’s battery finally beeped that it was getting low.  But, I wasn’t about to simply turn it off.  Nope, this thing was going to go until it died.  And about an hour later, at 56hrs and 52mins, it finally turned off.


Now, the FR910XT (like all devices with recent Garmin firmware on them) is designed to shutoff with a battery reserve.  This reserve is to ensure that the unit can properly shut down and avoid data loss.  In the case of the FR910XT, this is 3% remaining.  I haven’t tested the FR310XT in this same manner, but I would expect that it’ll probably end up roughly in the same battery ballpark as the FR910XT.

So, for a watch that’s ‘marketed’ to get 20 hours of battery life – I was pretty jazzed at getting 56+ hours.  Dang!

So what’s the only problem?  Finding something that can actually read a Garmin device file that long.  The TCX file is over 75MB! Most file TCX activity sizes are a few 1-2MB.  The compressed .FIT file is 2,000KB, again, most file sizes are 100-200KB.  For example, Garmin Connect fails on upload:


Sport Tracks truncates the first 35 hours (though, it does look fun up until that point):


But Training Peaks?  Well, it did the trick:


Here’s the graph file, though it too had some issues with data after 35 hours – which leads me to believe that the unit itself may have truncated the data.  But, to be fair, these tests were run on earlier beta versions of the firmware.  But TP did show the correct total time above, whereas Sport Tracks did not – so all is not lost.  In either case, I’ll probably try giving it another go once I have another 56 hours to kill without use of the watch.

You can see the up/down pattern of the sweeping ANT+ simulator.  I think I had changed the sweep rate a bit later on, hence the change in pattern.


But what about the Timex Run Trainer?

Well, it kept on going.

And going.

And still going.

No seriously, days later, it was still going.

See, the Timex Run Trainer’s limitation is really actually more memory than battery.  The unit is designed to last 8-10 hours in active GPS mode (where battery is the limitation), but lasts 6 weeks in standby watch mode (before the battery dies).  So around the 20 hour marker of recording data it beeped that memory was low, and shortly thereafter that memory was full.  Nonetheless, it kept on displaying my data without issue in real-time.

And in fact, it continued to do so – all the way up until 99 hours, 59 minutes and 59 seconds.


At which point, the unit partied like it was 1999, and stopped counting.  The unit simply didn’t know what to do after 99 hours, so it just hung out there.  Now it would keep on displaying ANT+ data, but no further tracking of time was occurring.

Nonetheless – let’s be clear – that’s really damn impressive.  And the biggest kicker?  The battery still showed full availability!  Yup, not a single battery bar had disappeared.

I’d reason/guess that if I left it there it’d probably go 4-6 weeks all-in while being turned on.  But, I use it with other tests and what-not, so it was back into the inventory it went.  But, if you were one of the extreme-nutcase folks that do not just the deca-Ironman’s, but the triple-deca Ironman’s (30 Ironman’s in 30 days), this watch would actually work for you.

All in all, I’m pretty impressed.  It’s pretty clear that for GPS watches, the biggest battery drain is indeed the GPS itself, and not the display.  This is of particular note for the subset of folks that ask about using the FR910XT/FR310XT as a day watch.  In short, if you simply turn off the GPS – it’ll last all day quite easily.

I’m also kinda curious now as to what the battery life might look like on other units with the GPS off.  Maybe I’ll save that for another rainy day…always gotta have a few rainy day projects around. :)

Thanks for reading all!

Actually, P.S.: For those curious about the Motoactv with the new and updated firmware from last week – I’ve been running some fun tests while on vacation.  The new firmware dramatically improves battery life from the previous 2-3 hours, to upwards of 8 hours. I did one today during a 14 mile hike that took about 6hrs, but kept it running afterwards just to see where it’d die.  It finally hit the mat at 8hrs 41m and 13s. 


This is in their new Marathon Mode – with the GPS enabled and a single ANT+ accessory (the footpod), which takes a sample every 3-seconds instead of every second.  Which is basically akin to Garmin’s Smart Recording Mode.  Not ideal for cycling power meters, but generally fine for everything else – and a massive improvement over the initial release.  More in this in the next few days…


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  1. The most ridiculous part of that deca-IM in Mexico is not the distance, it’s the fact that the bike and run are done on a 1.2 mile track. People start hallucinating, apparently. I wonder why…

  2. Thanks Ray, the best thing about this with the 910XT is for us ultra runners that do not want to carry a battery to charge during a race. Instead of using the GPS we can use the foot pod and get elevation data for long ultra marathons. For those shorter races (under 20h) we can keep the GPS on.

  3. Anonymous


    Can you run the test on the FR305? I’m looking for a way to get the 305 to last through an ironman bike/run.


  4. Ray,

    Thanks for your testing and posts. They are truly exceptional.

    Happy (and fast) 2012.

    Bob Mitera

  5. Thanks for the interesting test!
    The Run Trainer’s battery is so astonishing!

    And how could I do the ANT+ simulation by myself?
    Download the ANT+ Simulator from the following link:
    link to thisisant.com
    and use the usb stick from the package of FR405?
    Or I need a special ANT+ USB dongle?

  6. very cool post! Thanks for running the test to give us a benchmark. I gotta think Garmin and Timex have done these test but just choose not to publish or share since they cannot ‘gaurantee’ them and the ‘ultra’ communicty is quite small… regardless its a nice benefit of the watch. Appreciate you taking the time to do and share.

  7. Wow that is some TSS score for your Training Peaks! 3292!! Quite impressive:)

  8. The MotoACTV 8:41. is that with GPS on? or just with ANT+ devices/footpod?

    the battery on my 405 is getting weaker and weaker. Looks like I better run a sub 3:30 marathon in January, or it might fizzle out on me before I finish.

  9. “the unit partied like it was 1999, and stopped counting”. Tears streaming down my face!!!

  10. Hi Anon-
    RE: FR305

    Yup, I do want to do it with all devices, planning on it when I get back.

    Hi XMonkey-
    RE: ANT+ Simulator

    Yup, just a simple ANT+ USB stick from the FR405 (or other Forerunner) is what I use, works great!

    Hi Morey-
    RE: Motoactv

    Yes, that was with GPS – and an ANT+ footpod as well. Just updated the post to clarify it.

    Thanks all!

  11. Anonymous

    Great post Ray.

    With the new firmware updates that you mentioned are you now able to test the Motoavtiv for battery life with GPS on and Music playing?


  12. Anonymous

    thanks for that update Ray. Still no word on if the Timex Run trainer will have a firmware update to include Lap Pace yet? Its something no one knows the answer to


  13. ekutter

    Could you post the .fit file from the 910? I’d like to see if my personal software can process the file.

    With this info, it would be nice if Garmin added a watch only mode that made it feel more like a watch.

  14. gando


    When you used the motoactv with the new firmware and got 8 hours using the marathon mode, gps and foot pod did you have the screen timeout set to on or off? i.e. did the screen stay on the entire time or did you have it automatically turn off and then hit the power button when you wanted to see it?


  15. Hi Ekutter-

    Sure, no problem, here ya go:

    link to sites.google.com

    Hi Gando-
    RE: Marathon Mode Screen

    Correct, on/off based on my needs, I’d say I checked it every 5-10 minutes, which is obviously much less than if I was racing a Marathon. I’ve got it on my radar to do a test with GPS on, ANT+ on, and screen on entire time.

    Thanks all!

  16. Very nice and interesting tests. Concerning Timex Run Trainer test I think if unit had enough memory space for data it would use much more battery juice and it wouldn’t last so long. Writing data to flash memory uses quite a lot of energy. If Timex stopped to log data then after that point it operated in something like watch mode + sensors.

  17. Anonymous

    Does anyone know where to download the ANT+ Simulator? I’ve tried finding it at
    link to thisisant.com

    Do you have to be a registered($$$) developer to download the tool? Also the version you have in your article seems to be v1.8 but the only version I’ve seen is v1.6 in a forum post.

    Where do I download it ? Can someone provide a link.

    thanks in advance

  18. Hi T-

    You’ll need to signup for the (free) adopter developer program, which enables you to download the tools once logged in.


  19. Niranjan

    Awesome review, as ever! Like many others, am tempted by the Motoactv but the battery life is a dealbreaker. Would be great if you could do a Motoactv battery life test with screen on all the time (at minimum brightness, if they have that setting) with music, ANT+ HR strap and BT headphones on, which I guess would be a combo many users would be looking at. If it can last 5 hrs, I’d pick it up in a hurry. Else I’d wait for V2 or an extended battery option.

  20. monster265

    I have been in contact with Timex (H/W, F/W) and TrainingPeaks (S/W), their support has been very responsive.

    Recent Timex Q&A responses, information that the user manual does not provide.

    1. Recording – is the interval Sensor data is captured?
    Recording affects all saved data, whether it is chrono or interval timer modes.

    2. Smoothing – How does this effect Sensor data capture?
    Smoothing is for display only. Actual data is saved in the watch database.

    3. How can Recording and Smoothing combined be beneficial?
    Recording – increase recording rate to have more accurate track information or decrease to save memory (for longer workouts). Smoothing can be used to have smaller changes to pace, speed or altitude. Turn off smoothing to get a more accurate, yet jumpier data feed.

  21. Anonymous

    Thanks for doing this. I am in the process of possibly switching from the 610 to the 910xt and am trying to figure out how to deal with the lack of regular watch functionality. My question to you is whether you can set up a different sport “other”, set the fields to be e.g. time, altitude and date, and have all of the sensors (except altimeter) turn off automatically when switching to that mode? I am having a heck of a time logging into the Garmin site or I’d ask this over there. Thanks!

  22. Hi, can i know how do you delete the workouts if your memory is full? I have been going through the manual and it seemed like the only way is to reset the watch but they gave no instruction on how that can be done. Appreciate your advice. Thanks.

  23. Anonymous

    On the Forerunner 910XT if you turn off GPS and just have it as a watch how long will it last? and give the example below will it work??
    EX. I go to a race away from home (Wildflower) and do not have power. Can i wear it as a watch on the car ride Friday (no GPS and no ANT+), Race (with GPS and ANT+) then after race turn it all off and wear as watch back home on Sunday?

  24. Hmm, I’m not sure. The biggest issue in battery life once the GPS is off is really just powering the display. I’ll run a test here in the next couple days and see how it shakes out.

    • Jordi

      Hi..in watch mode (gps off) my garmin 910 battery lasts just a couple pf days bacause the Watchs ANT+ Is working all the time..is there a way to disable it?

    • No, the reason it only lasts a few days isn’t because of ANT+. Rather, it’s simply because the screen draws so much power and the watch wasn’t designed to be worn as a day to day wrist watch.

  25. Anonymous


    Thanks a lot for your posts!

    I’m going to do a 24h adventure race and I would like the watch to record as long as possible. I need the GPS to be on.

    Now to my question: How much would you guess using a heart rate monitor also would decrease the battery life?

    The heart rate monitor is just a nice add-on, so if it would reduce battery life by 1 hour or more I would definately skip it. But if it only would reduce battery life very little, like 15 minutes, I would consider using it.

    Thanks a lot for all your help!


  26. Great test! Do you know if you can extend the battery life of the Timex Run Trainer by decreasing the sample rate? Thanks!

  27. Ignacio

    Hi, thanks for this review.

    Did you finally have the chance to try (on the 910XT) turning off GPS and just have it as a non-sports watch (no ANT+ neither, no back-up light, nothing at all, just pure watch functionality) in order to see how long will battery last? It should be quite a few days… that would allow me to use it as a normal watch when I´m sick (e.g. strong flu) and can´t workout for many days.

    Thanks a lot, and keep on doing this great work on reviews!


  28. Eek, sorry, forgot about doing that.

    I’m travelling at the moment (and don’t have it with me), but can if I remember when I got back.

    That said, ANT+ itself (recording/receiving) actually doesn’t do much against battery (direct from Garmin). It’s the GPS and display that kills it.

    That said, you might pull in a touch more than that. Again, I’ll try to remember to test it out.

    • Tisztul_A_Visztula

      Actually I have just now finished a test with my 310XT. GPS was diabled, I chose “other” mode to make 310XT not search for bike sensors and just for sure I disabled HR sensor. I charged my 310XT to 100%, never used backlight and during the test I pushed the Mode button not more than half a dozen times to check how many battery bars are left.

      The test started on Sunday in early afternoon. I got two vibrations warning me about Low battery, but when 310XT switched there was no third warning, or I just did not catch it. I put it immediately to the charger and it showed 8% left. I switched it on an the elapsed time was 88 hours 44 minutes and 49 seconds.

      Assuming that 910XT and 310XT have the same batteries and the internal algorithms are the same when both GPS and sensor searching are off, it should be the same for 910XT.

      Anyway I can check it in a couple of days, because I bought a 910XT, too. Hmmm, maybe I started to become addicted to gadgets. :-)

  29. Ignacio

    Ok, thanks!


  30. This is a great post! I used this information in preparation for a recent 50 mile race. I used the Timex Run Trainer with HR and Footpod for the entire race – 12 hours and 45 minutes. Worked like a champ. Now, I am getting ready for a 100 mile race which will likely take 25-30 hours. It looks like this watch will work for that, too, but it will likely run out of memory and thus not record the full data set. Do you think I could remedy this by decreasing the sampling rate? I.e. only sample every 4 seconds (instead of every 2 seconds). Thanks!

  31. David

    Hope you don’t mind me troubling you but I can’t get the simulator to pair with my 310XT.
    I can’t find any info I can use anywhere else and there’s no help file.
    Could you run throught the steps necessary to pair it?

    • Assuming you’ve got the simulator open, and the ANT+ stick plugged in and ‘enabled’, then it’s a case of re-pairing your Garmin to the software. You’ll see a dropdown to select the sensor you want to use, and then the option to actually turn it on so it’s broadcasting. Once all that’s done, you’ll then search for a new sensor (HR, etc…), since it’ll be using a different sensor ID than your regular strap.

    • David

      Thanks for your reply it is much appreciated.
      I had done what you said above.

      Just found the info needed.
      It is here

      link to thisisant.com

      Hope this may be of use to someone else.
      Thanks for your help.

    • David

      and it doesnt seem to work with pairing mode enabled in the simulator which may have been the problem as the simulator seems to select the right settings when you choose the desired simulator.