- Polymer Lithium Ion Battery (LiPo) 3.7V 1100mAh
- Adafruit Micro Lipo w/MicroUSB Jack
- 3D printed chassis/case
- 1mm brass wire
- 22AWG wire
Bend some small pieces of the 1mm brass wire and glue them into place as per the photos. Solder wires from the the positive brass wire piece (right side, check battery compartment markings to be sure) to the BAT point on the LiPo breakout, and the negative side (left side) to the GND point.
The photos should sum it up, it's not a very complex build.
When you're putting the new battery pack into the Gameboy, you want to lower the bottom edge in first and push it against the lower springs to compress them, then the top part with the brass contacts should lower down in without scraping anything. When you let go, the lower springs push the new battery up against the contacts at the top, holding it in place.