My speed/cadence sensor from my Bontrager Node 2.1 has been - less than perfect, shall we say. The rubber band that holds it in place lets get it out of position quite a bit.

The most recent example was yesterday on a ride. I had a fall (weight shifted to my clipped-in side) and went over. It got bumped. I spent the rest of the ride trying to get it back in place, and it was mostly working. But I went back to the shop today and asked them to zip tie that little *!*#&$& in place so that it wouldn't do that again. But we were having trouble getting it working again, and they determined it was the battery.

So I've had the bike since the end of May, and I've only put on 490 miles according to the computer. Did I get a bad battery, or is that what I should expect for this sensor?

Assuming it uses a reed switch like the Garmin GSC-10, I would expect at least a year of battery life...UNLESS you park it with a magnet next to the sensor which holds the switch closed, then expect about a day.

Ah, so don't park it with the wheel magnet or the crank magnet near the sensor? Maybe I did that.

What sort of battery? If it's an AA or AAA, and you used the one that came in the box, buy a new battery. Manufacturers get specially made (cheap) batteries to ship with products so they can advertise, "Batteries included." The cost of cheap, in this case, is lifetime. These cheap batteries are made so they'll show the device works when it comes out of the box. Anything after it powers up is gravy.

It was a watch battery, standard for a sensor like this.

I've had mine since April and put about 2000 miles on it. It's still on the original batteries, head unit, speed/cadence transmitter, and heart monitor (which I don't use all the time).

Well, I'm not sure the battery was dead, but if it was I'm guessing I somehow drained it early.

Almost 2 years and 8600 kms on my sigma 1009 sts with original batteries

I've heard that, but am not certain if it's true or not. I have a number of bikes with GSC10 sensors and haven't had an issue with the batteries going dead prematurely. I think the circuit could be designed such that the battery wasn't drained by a closed reed switch, and it would be a significant engineering oversight if they didn't do that.

I have the Garmin GSC-10. I got 500 hours of riding time over a 2 year period on the original battery, and it was still working fine when I changed the battery.

Calculating:
'My Tourbook' shows that my average cadence (including coasting) is about 75 rpm. So for 500 hours * 75 rpm *60 min/hr = 2,250,000 pedal revolutions.

At appoximately 15 mph average * 500 hours = 7500 miles; a 23c wheel is about .0013 miles per revolution ( google '2100 mm in miles'), or 760 revolutions per mile. That's 5,700,000 wheel revolutions.

That's a lot of work for the battery!

I shouldn't have brag about it, last night on the way home the battery went dead. :-(