my copy of pokemon silver cartridge shipped with a bad save battery. i'd only be able to get to the fourth gym or so before the batteries in my gameboy would die.
Amazon.com: 12 Pack CR1616 Battery, CR1616 3V Button Cell Lithium Battery with Solder Tabs for for Pokemon, Gameboy Color, Gameboy Advance Game Battery Replacement : Video Games
How to replace a GameBoy cartridge battery without losing saved data
Soldered Battery to a Gameboy Advance Game PCB so it can save, it still does not want to save. | TechPowerUp Forums
Save Battery Holder for Game Boy Game Cartridge | CR1616 | Hand Held Legend