The CR2032 (or the DL2032)
Note: before changing the battery, record your odometer reading as that will reset with the battery change. Some folks like to take a snap shot and post it to Instagram as a way to remember what it was.
The Cateye computers use a slim watch battery, in most cases, it will be the ubiquitous CR2032. (Also DL2032
You can get this battery everywhere. You are not required to use any certain brand. I’ve had excellent results with the Energizer brand, but you can often get better deals if you stop by your local Battery Plus or by ordering bulk on Amazon (not that you need that many!!!)
Thanks to their auto-off feature, these batteries tend to last forever — years if you don’t ride that much. If you ride frequently, you might find that you need a new battery every year.
The real challenge, of course, is the install. You’ll need a coin to open the speedometer. The bigger the coin, the easier it will be to open it without chewing up the back. A large screwdriver can work, but it tends to chew up the case.
Once you get it open, having a small point to help pry the ring retaining the battery and the battery itself out is good to have.
This is especially helpful if there is corrosion. If you find a lot of corrosion, I like to dip a q-tip in Coca Cola and do a little quick cleaning and then use the other end of the q tip and some rubbing alcohol to dry everything up.
Install the new battery so that the flat “+” side is facing you. Then reinstall the retainer ring (you won’t get a solid connection without it) and the outside case.
The battery will work, but you will need to recalibrate it.
How to test the CR2032: The proper way is with a voltmeter.
It is a little weird, but you can test a CR2032 by licking it (not recommended). I find that sticking my tongue to the positive side gives a small, sharp taste or shock. It’s the least sensation, but it is a handy way I use to test them when in a pinch. Of course, don’t hold me liable if you burn your tongue with battery acid or something. I’m sure this testing method is highly discouraged by every manufacturer.