History:

A recent nostalgia crisis made me take my old Casio fx-8500G calculator out again. When A was a student, I modify it's power supply system because it was needing three CR2032 cells that was expensive and having a low capacity (to much black pixels on the screen was sufficient to drain them out of power) by a classical and inexpensive 9V battery (aka 6LR61).

The trouble with this solution is that the new cell was hanged outside the calculator by the wires that connect it to the calculator. Quite uncomfortable! So the idea to make a back-pack for my calculator to hold the battery.

Caution and notes:

Take great care of the polarity, a wrong connection can make you destroy your calculator!

To ease to battery removal I strongly recommend to add at least a piece of paper (pink on the photography) in the holder behind the battery. Ideally you can solder a ribbon to the holder.

When in position on the back of the calculator, this holder prevent the use of FA-80 interface. To use it, you'll need to unplug the battery, remove the holder and re-plug the battery without fixing the holder on the back of the calculator.

V2 on 2017/21/11:

Improvements :
- refined shape,
- pen holder for Bic Cristal (a cheap and reliable pen),
- a holder for the connector's cover, hidden because the interface FA-80 is not usable with the battery holder fixed on the calculator.

Possible improvement:

• adding a cap,

By the way!

It seem that enthusiasts conceive serial adaptor for the proprietary port on the left of the calculator. I'm not skilled about electronics and haven't the tools to make it but I can make enclosure....

Links:

• http://www.pisi.com.pl/piotr433/fx8000se.htm
• http://blog.damnsoft.org/rs232-ttl-adapter-for-vintage-fx-casio-calculators/ (note that if the connector is physically the same, their wirings are différent... too bad !)

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