A review of the Mega Memory Card for the Game Boy, Game Boy Pocket, and Game Boy Color.
Tested and works on: Game Boy Color Game Boy Advance GameCube Game Boy Player
Does NOT work on: Super Game Boy
About games with a dead battery: If you start a game, play, and save, you can quickly back it up before the battery dies on you again (as having the system on adds a little bit of charge.) Then, just restore the save the next time you want to play, and quickly back it up again once you are done. If you don't want the hassle of doing this, replace the battery after backing up your save.