I was wondering if it would be a good idea to connect the +5V and GND of the usb connection of a TI-84+ to the battery + and -. I would place a switch inbetween ofcourse (in case of willing to use with batteries and usb). The batteries deliver 4.8-6V (rechargeable and non-rechargeable), so the 5V of the usb would be the perfect voltage. I'm not really sure though, since it might maybe somehow destroy something, and I don't want that.

The reason I want to change this is because I only use my 84+ on my desk near my pc, and not even often, just sometimes for some gametesting for the forum here. I don't use it enough, so everytime I want to use it I have to begin a giant quest to find the needed batteries for it. With the usb connected, i'd just have to connect it to my pc and get started...

I was wondering if it would be a good idea to connect the +5V and GND of the usb connection of a TI-84+ to the battery + and -. I would place a switch inbetween ofcourse (in case of willing to use with batteries and usb). The batteries deliver 4.8-6V (rechargeable and non-rechargeable), so the 5V of the usb would be the perfect voltage. I'm not really sure though, since it might maybe somehow destroy something, and I don't want that.

The reason I want to change this is because I only use my 84+ on my desk near my pc, and not even often, just sometimes for some gametesting for the forum here. I don't use it enough, so everytime I want to use it I have to begin a giant quest to find the needed batteries for it. With the usb connected, i'd just have to connect it to my pc and get started...

I'm a little confused as to what you are going to do exactly. I see two options:
1. Strip a USB cord and stick that straight into the battery cartridge of the 84+
2. Internally wire the calculator's own USB port into the battery cartridge

For option 1, it would totally work without any restrictions. I believe the 84+ uses a max current of like 42mA and the minimum for USB spec is 100mA, so you should be fine.

For option 2, I have no idea what would happen. The ground of the USB is probably the same ground as the battery cartridge, so that probably wouldn't be a problem. But when you wire the USB positive to the battery cartridge positive, weird stuff might happen. I guess the only way to find out would be to try it. If it doesn't end up working, you could install a hook (I could make it) so that you can selectively disable USB so that the calculator doesn't actually try to connect to the PC/wall.

Protip: Replace the hex screws with philips heads when you're done.

But what if you lose it? It's easier to get hold of a philips head screwdriver.

Ok, I did the modification, and as magic, everything is working perfectly!

I connected the usb power pins directly to the battery pinconnectors on the pcb. It turns on, works perfectly, receives and sends data and can run everything as wanted. So my problem is solved


There is one strange thing though. In my device manager, it show that it draw 0mA current, which is rather strange. But I don't really care, it's allowed to have up to 500mA, which means that if you would run the 84+ on batteries, they would only last for 1-3 hours with that current draw..which is kinda impossible I think.