External battery holder for Casio fx-8000G and fx-8500G

thingiverse

A recent nostalgia wave hit me hard and I decided to take out my old Casio fx-8500G calculator again. When I was a student, I modified its power supply system because it required three CR2032 cells that were pricey and had low capacity - the screen's black pixels would quickly drain them of power. I replaced these cells with a classical and inexpensive 9V battery (also known as a 6LR61). The trouble with this solution is that the new cell hangs outside the calculator due to the wires connecting it to the calculator, which can be quite uncomfortable. So, I came up with the idea of creating a backpack for my calculator to hold the battery. **Caution and notes:** Be extremely careful about polarity - a wrong connection can damage your calculator! To make removing the battery easier, I strongly recommend adding at least one piece of paper (like the pink one in the photo) behind the battery holder. Ideally, you could solder a ribbon to the holder. When positioned on the back of the calculator, this holder blocks the use of the FA-80 interface. To use it again, simply unplug the battery, remove the holder, and re-plug the battery without attaching the holder to the calculator's back. V2 (2017/21/11): Improvements: * Refined shape * Pen holder for a Bic Cristal pen (a cheap and reliable option) * A holder for the connector's cover, which is hidden because the FA-80 interface isn't usable when the battery holder is fixed to the calculator Possible improvement: * Adding a cap