How to Keep the GPS Going Through a 24-Hour Endurance Ride

How to Keep the GPS Going Through a 24-Hour Endurance Ride

(Photo: Top of Immigrant, next to Watson’s Monument, 2015, with the Garmin and “hat hair”)

Want to keep your Garmin 310x Forerunner (or equivalent) alive during an entire 24 hour period without the battery doing what screen writers call, “fade out?” I simulated a ride and was able to keep my Garmin GPS going the entire 24 hours. Here’s how.

The Issue – The GPS Battery Does Not Last 24 Hours

Like many of us, I use my GPS to keep track of speed, distance and the heart rate on whomever would allow me to remain as a rider. But I found the instrument’s rechargeable battery gives-up after about 13 hours of use. This leaves those competing in long rides like the Tevis Cup and Old Dominion “in the dark” from information they may feel is crucial to their survival on the 24-hour trail.

The principal culprit of battery zapping is with the GPS’s incessant recalculating of its position. Some units recalculate every few seconds which causes the battery to rapidly deplete. On many GPSs, like mine, one cannot re-program the instrument to cause it to calculate less frequently. So, we are stuck with an instrument that cannot last the entire 24 hours without some sort of outside assistance or replacement.

There are few options around “dead battery syndrome.” One is to have separate GPSs along the way, each one freshly awaiting at the next stop. Another option is to recharge the GPS in-route. Yet another is to buy one of the $600-700+ ones that can last just about 24 hours if you reprogram it to calculate its location less frequently. Another option, of course, is to have a miracle finish, completing a 100-mile ride within about 12 hours from the start.

I chose to experiment with the second choice, to attempt to recharge the GPS along the way.

(Photo: Garmin 310x Forerunner and Fritelsa 20000mah Power Bank)

 The Equipment

The GPS: Garmin 310x Forerunner, purchased from my friends at  The Distance Depot in 2014.

Side story – Here comes the part where, much like the Tappet Brothers’ “Car Talk,” technical issues are interlaced with sensitive relationship matters.

I bought this particular GPS as a gift for a lovely friend who, before I could give this to her, shattered my heart. The GPS remained in my possession several months thereafter, gift wrapped, until finally, I mustered the courage to open it.  “Oh, a Garmin GPS! For me?”

The Charger: Fritesla 20000mah Power Bank 4USB Portable Charger (purchased recently from Amazon).

Note: Some portable power chargers will not charge a GPS. This one, the Fritesla 20000mah, does the job even though the instructions say it may not. I’ve not tested other portable power banks to determine if they would charge this GPS. I did not test other GPS instruments with this power bank.

Whatever brand portable Power Bank you might consider, these are handy items and slip easily into awaiting crew bags. The one I chose can charge both a cell phone and the Garmin simultaneously.

The Methodology

I started with a fully charged Power Bank and fully charged Garmin 310x. I employed the heart rate function but did not have it connected to sensors. Four separate toggle-through windows remained on.

The Data

I started the GPS as if I were on a ride and kept it running. Following seven hours I turned off the GPS and plugged it into the power bank. The GPS indicated it had 61 percent in charge left in the battery before recharging commenced.

Following 40 minutes of charging I removed the GPS from the power bank, turned it on and reset, storing the info I had accumulated in case there was a failure later down the trail. The GPS charged-up to 93 percent in this first 40 minute period.

After another seven hours, I repeated the charging process with the Power Bank. Before recharging, the GPS indicated it had retained 54 percent of its charge. Following another 40 minutes of charging, resetting to store (and not lose) data, the GPS indicated it had charged to 88 percent of its potential.

I checked the GPS 10 hours thereafter. It remained alive with a remaining charge of 36 percent.

I repeated the testing and came within 2 percent of all reported percentages.

Additional Info

During this test, I did not use the back light to view the screen. The back light zaps the battery further.

As most all are aware, the final hours of the Tevis and Old Dominion are ridden in darkness. I recently rode the Tevis course in the full moonlight, from Robinson to Driver’s Flat, 7:30 p.m. to midnight. I was not able to see the Garmin screen with available natural light (the moonlight). I could see the screen by turning on the GPS’s back light or when I briefly turned on a headlamp.

Further assumptions

Why did I use 40 minutes of charging and not a whole hour? I assumed when a rider is vetting-in on a one-hour hold during a 100-mile ride, the maximum time she/he may have to mess with a GPS would be about 40 minutes. This time could be shorter or longer depending on distractions and efficiencies of the rider and crew.

Why did I recharge twice at seven hours? I assumed an approximate seven-hour cutoff time on the first vet-hold on the Tevis Cup. Riders must be “in” at Robinson Flat no later than 12 noon. And the cutoff at Foresthill, the second vet-hold, is another seven hours (from Robinson) where riders must be “in” at 8:30 p.m. I also assumed these may be the only times one could recharge with a portable power bank.


1. Gordie’s three-year-old Garmin 310x can last the length of a 24-hour ride so long as it receives two 40 minute charges at the two simulated one-hour vet holds and without engaging back-lighting.

2. We do not know whether charging would be better with the instrument turned “on” or “off” when charging. On mine, the only way to read what percentage of charge is left is to charge the GPS while it remains off.

3. We do not know whether the lack of a recorded heart rate impacts battery depletion.

And, (here comes that Car Talk conclusion).

4. It seems the charged Garmin survives longer than a depleted relationship, the very one, in this instance, that this instrument’s heart rate function was meant to nurture.

That’s the scoop. Until next time, remember, it’s all about The Write Choices.

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