Use a 3.8mm SNES security bit screwdriver to remove the screws from the cartridge. The cartridge shell should easily separate. There are two screws used during this step.
There are no tabs holding the board in place, it rests inside the cartridge. Lift the board from the shell.
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.
Flip over the board and solder the new battery into place. I always recommend using a bit of flux when soldering.
Using the 3.8mm SNES security bit, screw the cartridge shell back together. There are two screws used during this step.
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.