New battery causing OS drama, "error updating firmware"

[Charla]

Hi, I haven't been able to find any joy solving this via Google, so hoping one of you clever clogs can help me.

I've installed a new battery (from a battery store, as reputable as I could find) in my Macbook Pro mid-2010 17" unibody. Starting up I get the error "macOS could not be installed on your computer. An error occurred while updating firmware".

I have reset the PRAM and the SMC but to no avail. I am able to start in Safe Mode, system information detects the battery at least and First Aid finds no problems.

Not really sure what to try next but really hoping there's a solution! Currently running 10.13.6

Thanks so much in advance.

(also, oddly, I tried to run the installer for the 10.13.6 update in safe mode, which is the version I'm currently running, but the installer says "the volume does not meet the requirements for this update". Plenty of space available. A clue?)

 

[Charla]

Problem solved. From that same failed install screen on startup, I was able to define the startup volume. Hadn't realised the mouse would reveal menu bar options up the top. Sorry, should have thought of it earlier. Just thought I'd post this in case anyone else has the same problem.