Different but related problem and solution here: Bought a used 2019 Volvo Xc90, and everything went well… Then I found something that looked like a wireless dongle in my car, and I had no idea what it was. It was about the size and shape of a normal USB dongle, except the USB part.

After some research, ai found out it’s something called “sports key”. It’s waterproof down to 60 meters, contactless, and allows me to use my car as normal without the regular (and much larger) keyfob, as long as I have it on me. After testing I concluded that the battery didn’t work.

A few days later I had a followup conversation with the seller (a chain with good reputation) about an unrelated issue that they would take care of at no charge as part of the warranty. I then mentioned the sport key.

Turns out the sport key wasn’t covered by warranty due to the battery being designed to last three years only. I could order a new one for roughly 400 EUR. Pitty, it seemed like I had finally found something that was perfect for that tiny inner pocket on jeans.

So I did the only thing reasonable: I used various tools and violence to force it open. Yup, turns out that it was just a CR2032, of which I have many laying around. New battery, some tinfoil, and epoxy glue, and it now works like a charm. I doubt it’s waterproof down to 60m, but I tend to stay on land.

And this tiny key is permanently in whatever jeans I’m wearing, so don’t have to worry about remembering the keys either (I didn’t lock my old car for years, with the keys in the ignition, so actually caring about keys is new to me)

EDIT: Here it is, with a USB drive for scale:

I’d go as far as saying it looks pretty good.