Great news everyone! I've fixed the USB port and completed the project!

Second Battery Updates:
Not a whole lot here has changed, the main difference is I've used Kapton tape to isolate it from the PCB and I've covered the battery contacts in tape. I've also secured it to the PCB so it doesn't jiggle around at all.

Wireless Charging Updates:
I've basically redone everything on the inside and did it right this time. I received a wide variety of soldering iron tips which made soldering in such tight places much easier! Who knew that the right tools would make a job much better? Laughing

First, I de-soldered the wires from the USB port and cleaned up the connections. I made certain there were no shorts in the port then I plugged it into my computer. Voila! I've never been happier to see TI Connect CE bring up my calculator's contents! I immediately backed up all the files on the calculator and ran a USB self test which it passed with flying colors!

(As usual, click for full size)

I'm still unsure why the USB port didn't work even if unconnected wires were on it, but I'm just glad it's fixed now. I then soldered the wireless charging leads to the charging station contacts at the bottom of the calculator which I should have done in the first place! Finally, I wrapped everything up in Kapton tape and I closed up the calculator. Fortunately, it works even better than new! The wireless charger works, so does the second battery, and the USB port is fixed.

There is something a bit odd with the wireless charger. For some reason when I put it on my new charging pad it makes the pad emit noises like chirping or sometimes a tone. It's not very high pitched which is what confuses me. It doesn't make any noise at all when I put just my iPhone on it. My best guess is maybe the receiver inside the calculator is too far away since the charging pad didn't emit noise when I was testing the receiver outside the shell. The only negative effect I've noticed is the charging pad and the shell of the calculator are warm where the coils are. The temperatures aren't even close to alarming though.

Backlighting Keys Update:
I think I'm going to hold off on this one for now. It appears that I just can't find small LEDs out there that are bright enough without drawing a ton of amperage. Even if the batteries can handle the load, I'm not sure I'm comfortable with how much they heated up during my tests. That's not to say I'll never come back to this again, I'll just have to look deeper, or get a 3D Printer to create thinner keys (which is more likely to happen).

Unless there's something drastically wrong with with what I've done, I'm going to call this project complete. Would I recommend doing any of these mods yourself? I'd say no to double batteries due to the risk of something going drastically wrong. However, the wireless charging mod actually isn't dangerous if you do it the right way. All you need to do is cut away the shell to make room for it, secure it to the back shell, and solder the leads to the charging station contacts which hardly anyone here uses anyways. I may even do it to my own revision M CE. I had a lot of fun with this project, even if I got scared to death last post. I'm looking forward to trying more modifications in the future!

I have considered adding built in recharging into Casio Prizms (FX-CG10/20/50) but was not sure how to do it - the calculator has 4 removable AAA batteries and supposed to work on both alkaline and Ni-MH baateries (changable in the settings) and it has a mini usb port for data transfer with the calculator acting as slave device but does not charge batteries as far as I can see - what would be necessary steps and parts to make the Ni-MH batteries charge in the the calculator when it is connected to a usb power source via existing USB port on the calculator please?
I'd suggest creating a new topic amazonka, it's quite an interesting project!

I do forsee a lot of issues though
  • I highly discourage soldering anything directly to the USB port, it can cause data transfer to fail.
  • Even if soldering to the USB port works, you'll probably need to find a way to disconnect the calculator from USB power while charging the batteries.
  • Rechargeable battery chargers have a lot of bulky components inside. I don't know how much space is free inside the Prizm but you could easily run into clearance issues.
  • The batteries are probably hooked up all in series so you'll need to connect each battery to the charger separately and potentially find a way to disconnect each battery from each other while charging.
  • I doubt you'll be able to use the calculator while charging which is probably the whole point of this project.

I'm not sure it's worth the trouble to try and get AAA charging implemented. Perhaps you can find a Li-ion battery of the correct voltage and implement a small BMIC. I don't know where you'd connect the charger if not on the original USB port though.

As I've proven in this thread, I'm no hardware expert so don't let this shoot down your idea. Just be sure you're thinking of potential issues and be sure you can find a way around them! Good luck!
All good points, thank you. I will resurect a post where I first planned to have this as part of a slightly bigger project - and share your insights. Thanks again
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