i bought this GBA cartridge from a flea market recently and went home to try it. after playing for 5 minutes i saved the game and shut off the player just to see whether the save system works, and it didn't. i assumed that the cartridge was corrupted due to disuse or something like that and intended to throw it away, but i did a quick search online before i tossed it into the bin and i found out something that i didn't know before:
that there is a battery inside the cartridge that actually powers the RAM/EEPROM (or whatever the chip is) inside the cartridge. if that battery ever goes flat, you will be unable to save the game. a friend of mine did mention this to me before but i didn't think it was true because that would mean that one day when the battery does go out the cartridge would be useless, but he was right! i wonder how many people have thrown away perfectly good cartridges when a simple battery change would've done the trick...
i read online that apparently only pirated game cartridges have batteries, but this cartridge came in an original box and the screw that holds the cartridge together is the three pronged kind that comes with original nintendo gameboys, so i'm guessing some original cartridges did use batteries to save games.
anyway, after doing a few minutes research online i found out that the cartridge is powered by a 3 volt battery which is similar (if not exactly the same) as a watch battery. i bought a battery from a hardware store for $2SGD (which is the same price i bought the cartridge for!!) and went about dismantling the cartridge.
i saw online that they sell new batteries that come with the metal contacts for $10USD++ which is insane. i reused the contacts by ripping them off the old battery, but take note that it requires quite a bit of force as they're stuck to the battery pretty well.
the only problem i faced was that since i reused the metal contacts i had to attach them to the battery somehow. one of the ways i read online was to solder the contact directly onto the battery but i didn't like the idea of exposing a battery to a 200 degree heat source so i jury rigged it by using blu-tack! it was probably the most shoddy work i have ever done so far but hey...it will stick forever unless you throw the cartridge against a wall in which i think a disconnected battery will be the least of your concerns.
i realized that i bought the wrong battery size but it didn't matter in the end because it still fit back into the cartridge. the original battery is CR1620 whereas i bought a CR2025 which is bigger but it's all good...now the battery will last even longer than before.
i powered up the unit with the cartridge slotted in and saved the game before shutting it off. when i turned it on i saw that my savegame was still there so there you go, a simple and easy way of fixing your 'corrupted' cartridge.