Got a new (to me) car a few weeks ago. I'm really satisfied with the purchase, and the dealership was excellent enough to offer warranty as if the car was new instead of 6 years old. (It's a reputable "official" Volvo dealership).

The only thing that warranty didn't cover was the "sport key", as the battery was inly designed to last three years. Basically it's a contact less key that, if you keep it on you, you can open and operate the car without the much larger standard key fobs. Quite handy, as it fits perfectly in that tiny pocket inside normal pocket on standard jeans, and it's waterproof.

I really wanted mine to work, and getting a new one programmed would cost me roughly 400 EUR. I decided to attack mine with various tools of violence tosee if I could sort it out myself.

And yep, I could. It was a standard CR2032, and after applying a new battery, some tinfoil, and a bunch of epoxy, it worked like a charm. It's probably no longer waterproof down to 60 meters, but I don't really need to remember car keys in the morning anymore.