Replacing the battery on a Game Boy cartridge

I hang out in /r/Gameboy/ a lot and I see that quite a few people mention J4U or japan_4_you on eBay as their resource for buying Game Boy related stuff. They have a lot of good stuff and some things are just dirt cheap! While browsing I found Japanese releases of Gargoyles Quest ($6.50), Mole Mania ($5), Mario’s Picross ($2), Yoshi’s Cookie ($1.30), Donkey Kong Land ($3.20), Golf and Tennis ($1 each). I decided to buy the whole bunch and threw in Tamagotchi for $1 because of the white cartridge, even though I won’t be able to read anything.

It took about two weeks for the cartridges to arrive. The cartridges are in decent shape, they have some discolorations, some have markings and they all play after the mandatory blowing into the cartridge 😉. Actually all but Yoshi’s Cookie, which doesn’t work in my DMG, but plays fine in a GBA, so I can’t really blame the seller.

During my testing of each of the carts, I found that Picross and Mole Mania wouldn’t save anymore, which shouldn’t come as a surprise as the batteries are more than 20 years old! I anticipated the batteries would be dead so I had already ordered some CR1616 coin cell batteries with solder tabs from AliExpress.

Did you know that the name of these batteries describe the width and height? 1616 means 16mm diameter and 1.6mm thickness. Likewise the ubiquitous CR2032 batteries are 20mm in diameter and 3.2mm in height, cool right?

I opened up the cartridges and desoldered the batteries. The tabs on the batteries I ordered are slightly different and instead of just rotating the battery I opted for bending the tabs and making a really ugly contact. I feel like such an idiot, but I guess we learn every day!

At least the games save again!