For this job you’ll need a tri-wing screwdriver, a CR1616 battery (with solder tabs), a soldering iron and some solder. If you plan to clean the cart pins while you have the cart open then some cotton wool buds and electrical contact cleaner.
I already had a tri-wing screwdriver and managed to find some CR1616 batteries in a local electronic parts shop. The solder tabs were a bit thin, as you’ll see from the images, but they worked. I could definitely see the tabs snapping if manipulated too much. If you’re in the US then the batteries on Console5 look to have decent tabs, they also sell the tri-wing screwdrivers. Otherwise, this stuff is all available on eBay.
Using your tri-wing screwdriver remove the screw from the back of the cart. The front of the cart can then be slid downwards.
Lift the front of the cart off while being careful not to break the little tabs.
Heat your soldering iron up and take the board out of the case. Use the tip of the soldering iron to heat up the leg of the battery while using your other hand to gently lift the battery off the board. It should come away quite easily.
Do the same for the second leg and as you lift the battery off the board take a mental note of which side is positive. On both of the games I did positive was facing down.
Freshen up the solder points with some more solder and then place the new battery on top to get an idea of positioning.
Use pliers to bend the tabs into position and then check it against the board again. I had to be careful here with the legs as they were so thin.
Tin the end of your soldering iron and then solder the legs into place. You shouldn’t need much heat.
That’s it. Place the board back into the case and then fit the front of the case back on – starting from the slid down position and pushing the front back up.
Put the screw back and slide the cart into your Game Boy Advance of choice. Play a few levels of the game then check that your game has been saved. If all went well the save point, or continue option, should still be available after power-cycling the Game Boy.
If you were paying attention you’re probably wondering why I’d bother replacing the battery in a couple of bootleg GBA carts. Well… I got these carts with a GBA bundle a while back and both Kirby and Gunstar Super Heroes are amazing games. I’d rather keep them alive than throw them away, and I don’t mind having a few bootlegs in the collection if they’re just for me to play.