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My relatively new Garmin GSC 10 Speed/Cadence unit has started losing connection to my Garmin 500. I'm assuming that the battery is running out, since I'm still using the original that came with it. I have done about 35 hours of riding.

So I am wondering: how long should a CR 2032 battery last?

I know this is a little subjective and will depend on ambient temperature and to a lesser extent speed and cadence for transiently illuminating the LED each pedal stroke/wheel revolution. But generally, how many hours can I expect to get from a battery?

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In general, I've found "cyclometer" batteries to be good for at least two years -- maybe 100-300 hours of riding. My experience with wireless is limited, though (maybe 50 hours total) -- the transmitter may run the battery down more rapidly. (It would be good if several people would report their experiences here, to gather some sort of consensus.) –  Daniel R Hicks Mar 3 '13 at 14:54
    
Agreed, I don't think I ever replaced the battery on my old wired transmitter. Probably over 5000 miles. I'm not sure what to expect from the wireless transmitter, especially because it's transmitting from the rear wheel. Maybe more powerful = shorter battery life. –  kmm Mar 3 '13 at 15:17
    
1 - 2+ years on various Garmin cadence/speed sensors. –  Ken Hiatt Mar 4 '13 at 3:59
    
I not long changed the batteries on this very sensor after about 15 months and a couple of thousand miles. However I use this sensor on other bikes too, some of which are still going strong after 2+ years. Out of interest you I also changed the battery on the HRM recently, got about 3 years out of that. 35 hours seems low. –  PeteH Mar 8 '13 at 9:29
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3 Answers 3

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Right now I am at 159 hours of riding time on the battery which came with my GSC-10.

Garmin's stated battery life for the GSC-10 is 1.4 years at one hour of riding per day which works out to 511 hours. (See page 51 of the Edge 500's Owner Manual)

On the interweb I've come across two different suspected causes for low battery life on the GSC-10:

  • Some (mostly older?) GSC-10's are susceptible to corrosion due to incomplete sealing of the circuit board inside the GSC-10. If this occurs battery life is shortened due to an internal short which causes the battery to drain more quickly than normal.
  • If you store your bike with either the cadence or speed magnet lined up with the sensor, the GSC-10 may not go to sleep after a short period of inactivity like it is supposed to. This seems to result in faster than normal battery drain.
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I've had my GSC 10 since 2008. I used to get about 1 to 2 months out of name brand CR2032 batteries, but have since switched to Harbor Freight batteries. I get about 4 to 6 weeks out of these (a four pack of these costs about the same as a single name brand battery). Like you said, it all depends on your riding habits and environment though. The above is based on ~30 miles per day @ ~15-18mph and ~80 to ~95 rpm on average.

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My experience with the GSC10 (though with an Edge 305 not a 500) has been that the batteries last 6 to 12 months, or roughly 2500 to 5000 miles of riding. That works out to something like 125 to 250 hours of operation. That is considerably less than what is stated in the manual, but in the ballpark of what the other two answerers experienced.

The symptom you described (losing connection with the Edge 500) is consistent with a dieing battery. However, another cause could be poor alignment between the magnets and the sensor. I've found that the cadence magnet, in particular, will not be sensed if it shifts by a centimeter, or so. Since the Edge 500 can compute speed from GPS data, it's sometimes difficult to tell whether the GSC10 is really not sending data or simply not sensing the cadence magnet. Make sure the cadence magnet is aligned with the embossed groove on the side of the GSC facing your crank arm.

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