I recently needed to change the batteries in our garage door opener remotes. While at the store, I guessed (correctly) based on memory and appearance that I needed a CR2032 coin-style battery. The alternative was the similar-looking CR2025.
These CR2025 and CR2032 are both 3V lithium batteries that are identical in diameter. When I returned home, I actually found an unopened pack of CR2025 batteries in the kitchen cabinet so I did a side-by-side comparison.
As it turns out, the only thing that differs between these batteries is thickness (and hence capacity). The CR2025 is thinner than the CR2032, but they otherwise seem to be interchangeable — assuming you can make them fit your device equally well.
The thicker CR2032 is typically rated for 240 mAh whereas the thinner CR2025 is typically rated for 163 mAh.
Thus, the CR2032 will last somewhat longer than the CR2025 under otherwise equivalent circumstances. And of course the CR2032 may be too thick (or the CR2025 may be too thin) for your desired application — though there are possible workarounds.
For example, I needed a new battery in my Suunto heart monitor chest strap last night and had already used the CR2032 batteries that I had bought. Thus, I used a CR2025 and “shimmed” it into place with a small piece of folded-over note card.
While I’m not planning on this as a long-term solution, it worked in a pinch.