Preservation project. I'm upgrading old NES and SNES cartridges with better eprom batteries and battery holders. You'll lose your save games with the mod, but get years more use from old games.
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SNES cartridge battery : r/snes
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Replacement Save battery for Secret of Mana! : r/snes
Game card for Earthbound - RPG Game Cartridge SNES US Version English Language Battery Save Game Cartridge SNES: Nintendo Super NES: Video Games - Amazon.ca
How To: Replacing SNES Cartridge Batteries | Hey, it's that dog!
Replacing batteries the right way! : r/snes
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How to Replace a Super Nintendo Cartridge Save Game Battery - YouTube
Voltrax Retro Super Games 121 in 1 Multi Game Cartridge for SNES - 16Bit Classic Game Consoles: Super Nintendo: Video Games - Amazon.ca