I have just tried a different battery in it and no change

I will buy a new battery just incase.. not expensive
One thing that I have tried... when the screen goes strange when I think that I am in BIOS I pressed F10, F11, F12 and then ENTER. To emulte that I have been in BIOS and saved changes, it then re-boots. After then splash screen instead of it showing the error it just stays as a black screen.
The only way to stop it is to clear CMOS and then i'm back to the begining