Flip the board over so the battery is facing down.
Use a soldering iron to heat the old solder that holds the current battery in place. Remove the melted solder with a solder sucker. When enough has been removed, the battery can be wiggled loose.
Fit the new battery inside the SNES battery slot.
You'll need a this CR2032 battery with pre-soldered tabs for this step. Be sure to line up the positive and negative ends properly. Use the images in this guide for reference.
I'm using a CR2025, which will technically work, except that it has slightly different tabs that will need to be clipped. We had some left over after replacing a Game Boy cartridge battery.
Who's up for some NBA Live '97?
It's time to test your progress. Load up your SNES game and play enough to warrant a save. Our goal is to create new save data on the cartridge. After you save the game, restart the SNES and see if it loads.
Congratulations! You've added a few more years to the life of your SNES game.