The previous hardware worked fine. I used WIFI for the internet connection, and it also worked fine. I have a 4G SIM Card that I usually use when traveling, and I think it would be nice to use this instead, so the system will be entirely solar-powered, not depending on my home network.

Unfortunately, the charge controller USB port is not very good. According to this website:

The port can really only deliver about 580mA before the voltage falls too far.

And it turns out that is true. I can’t get my USB 4G WIFI dongle to work. I could have just tried to find another module to drop the 12V voltage to 5V, but I decided to buy a better controller. After changing the controller, the USB 4G modem works.

I also planned to use the solar module to power more stuff, not just this Pi, so I bought another solar panel, which is 100W this time. I purchased another battery to replace the small one. It was 5A, and now it is 60A. These changes should be enough for future expansion.