Before you open the case of the camera and potentially break a part, you may want to consider the file system format technique described on the link above. I have not had success with that technique myself, but it seems safer than opening up the camera.
If you’ve exhausted all possibilities and want to change the battery or SDCard, you can look at this topic:
There’s more details here on a guy that also had a circuit board problem, which he AMAZINGLY fixed. Incredible, but likely beyond the ability of most people. I would not be able to replicate his work.
Though it seems like if the battery is bad, not the main board, it’s an easier replacement.
I have not attempted this.
Also, I think you may be able to find a specific THETA SC teardown video or blog post.