It’s not a battery, it’s a capacitor. And yes, you can change it by soldering it off and replacing it with one from a junk board off ebay or something. If you can find the specs, you may find the component by itself, but Fuji won’t provide it because they rarely receive individual components.

As a former Fuji tech, this break down is about 80% correct. I would not recommend ever removing the CMOS sensor from the lens unit. They are shimmed and calibrated using computers and you run the risk of throwing your focus completely out of whack as well getting dust on your sensor. I also see no mention of discharging the flash capacitor. Unless you like getting shocked, I would recommend discharging it before sticking your fingers or any metal object in the camera. One wrong touch will not only shock you a bit, but also short out certain components on the board if you’re not careful.