Electronics, Lighting, & Gadgets - How long does speedometer battery last?

I bought a cheap ( but excellent ) Schwinn bike computer for just $9 three months ago. I have now used it for 1500 miles and notice is sometimes fails to register speed. If I fiddle with the magnet it starts working again. Is this a symptom of low battery or bad magnet placement?

The easiest thing to do is buy a new battery and try it. Most electronic circuits will work after a fashion and likely intermittently when the power supplied has lower than a certain voltage supplied, in your case from the battery. Your question of 'how long does speedometer battery last' is irrelevant since you likely do not know how old the battery was when you bought it. They have a shelf life so old batteries even though unused are lower than normal capacity. Just get a new battery. A dollar to a donut your problem will go away.

I've had the same problem. Do you leave your bike in a bike rack at work, where other bikes are placed and removed as well? Those bikes, bumping into yours, might be the cause. It used to be my problem, until I just agreed to sit my bike against the side of the rack. Just as safe, but not in between people not caring about the value of your bike.

Try cleaning the magnet and sensor.

Try cleaning the magnet and sensor.

Don't think that will matter too much since they're magnetic, but I would align it better and tighten them both. The magnet has to come very close to the pickup for it to register.

If the magnet can rotate at all on the spoke or slide a bit, you can definitely get dropped signals.

The battery could also affect reception, but I'd fiddle with the magnet first given the symptoms.

I bought a new CR2032 batter yesterday for $3 and it seems to be working better, but still drops occasionally. I will tighten the magnet and re-align it as close as possible to the sensor.

I bought a new CR2032 batter yesterday for $3 and it seems to be working better, but still drops occasionally. I will tighten the magnet and re-align it as close as possible to the sensor.

I assume this is a wired unit? If it's wireless, bear in mind there are two batteries, one in the sending unit and one in the computer itself.

Otherwise, good luck with aligning it. It's not too hard.

I have a couple of these Schwinn units. One I bought nearly two years ago does real well. One I bought a couple of months ago has been doing the same things the original poster experienced. The battery in the newer unit is a little 386 instead of the earlier, larger 2032. I have not taken time to do much with it, yet. It is a wired unit.

I've been adjusting the magnet, but it still seems temperamental. My theory is there is some piece inside the sensor that is getting stuck. When the magnet goes by it I can hear a faint ticking sound when it works. So perhaps that piece gets stuck sometime?

Just an update it seems to be working fine now. I adjusted the magnet so it passes as close as possible to the sensor. Then I tightened a lot. So far no drops in 45 miles.