Hello,
So I recently picked up Pokemon Gold on eBay for super cheap because the saving feature was broken. For those of you who don't know, Pokemon Gold and games like it store their saved data in a special kind of RAM called SRAM. Since RAM requires a battery to keep the data intact, these cartridges have a small battery inside. Usually, when your game stops being able to save, it's because this battery died. Unfortunately, the kind of battery they use can be difficult to find. I decided to use an alternate battery in its place - a AA.
Obviously a AA battery can't fit inside of a GameBoy cartridge, so I had to do a lot of hacky stuff to make this work. The first thing I did was scrounge up some equipment. I don't have any solder, or a soldering iron, or even any proper wires. The materials for this build are as follows:
-Cheap plastic pen
-Lighter
-Old noise-cancelling headphones
-Speaker wires
-Tape
-Scissors
-AA Battery

These are all the materials I used for this. The first thing I did was get the cartridge open. I took the ink and metal tip out of my pen, and melted down the tip. While it was still hot, I pressed the tip of the pen onto the screw that held the casing on (it requires a special screwdriver that is difficult to find). After the melted plastic pen dried, I had a DIY GameBoy cartridge screwdriver. I removed the screw and opened up the case to reveal the game inside.
Attached to the game was a battery powering the SRAM. I pried it out of its casing, leaving the contacts in place. Then I looked for some wiring and found speaker wire. This I stripped. I wound some of it around each contact and left it aside. Then, using the lighter to soften the plastic, and scissors to manipulate it, I put some holes in the side of the casing so the wires could get out. I put the game back in the case and led the wires out.
I went to look for something to hold the battery with. After a lot of searching, I stumbled upon some old noise cancelling headphones that had a mount for a single AA battery. I abused the headphones until just the mount remained, and put a fresh battery inside. I trapped the leads coming out of the cartridge between the battery's contacts and the walls of the mount. I then stuck the cartridge back into my GameBoy Advance and turned it on.
I went through the prompts and chatted up Professor Oak a bit, then finally was dropped into the overworld and saved the game. I turned off the GameBoy, crossed my fingers, and started it up again. Hooray! The game offered me the option to continue, and I was able to save again.

Pics of the build below:

The GameBoy showing the successfully saved game. The front of the case is to the left, only half of the case is actually inserted. This allowed me to make sure that the cartridge meets the contacts in the GameBoy itself, but still let me meddle around inside without taking it out.


The game, before replacing the front of the cartridge.


The cartridge and the battery leading up to it.


The final game, completed and ready to play!

Intriguing repair. Since the call on a button battery (I'm guessing that's what they use in those?) is so low, that a AA should last for pretty much ever.

So long as it works though, that's all that matters I guess.

Yeah, they use a CR2025T battery. The AA will pretty much last me until the wires get loose.

Nice. I was under the impression that they would use a 3V lithium for long lifespan. Though, since that kind of RAM needs so little power, I would imagine that a single AA's voltage might be enough to operate it okay (though two in series might be safer).

I have yet to have my old Gameboy games' save batteries die, but I was able to fix a problem with a Pokémon Blue cartridge several years ago by finally finding a way to remove most of some particularly stubborn black stuff on the contacts (it frequently lost saves due to bad contacts—the Pokémon games in particular seem especially prone to losing/corrupting save data in these cases).

I was going to use two AAs, but I couldn't find a case that could accommodate two batteries. I was originally going to super glue wires onto two different batteries (I have no solder), but it was troublesome, so I tried using one instead.

Very nice fix. I can play all these games on an emu on my PSP but it's still very cool to make the old stuff work. If I were you, my next project would be building a usb reader so you can rip saves from the SRAM. Do you have an arduino?

I do not, unfortunately.

Hmm, nice! I haven't ever had a game die like that, but I did have one once that had a cracked PCB (It's gone now, fortunately it was still under warranty) which sometimes loaded corrupted games and sometimes just marked the save data as empty

It was glitchy in so many ways.

Nice hack. Did you say how long it took, and I just missed it? Else, how long did this take to finish?

I happen to have a spare CR2025T battery, for some reason, and I am wondering, what is the special screwdriver that you used?

He melted the end of an ink pen, and before it cooled mashed it against the head of the screwdriver, if I read that correctly.

Well softened, but w/e

He made his own screwdriver by melting the tip of a pen.
Ninja'd

I did that on a gamecube, and promptly replaced the screws with phillips ones because of how horribly it worked.

A tip: don't take the pen off the screw until it has cooled!

This took me a couple of hours to do, and most of that time was spent finding materials (I had no idea what I was going to use for this when I started). I just had an initial vision of sticking two AA batteries on the top of the cartridge, and turns out a single AA works fine, too.

And yes, you can get a temporary screwdriver for three or four uses by melting the tip of a pen and molding it onto the screw you want removed.