Having 'played' with a few auto darkening helmets I did discover that they generally rely on a 3 volt lithium cell to operate.
Stands to reason that a low or dead cell will give poor performance.
Having learned that tidbit of info I always hang my helmet near the window so as to keep the cell fully charged.
Naturally if you do a lot of welding the ark keeps it fully charged.
And, yes, welding under a bright light source helps a lot.
I have a Miller helmet and the same coin battery has been in it for 7~8 years and never an issue.
My helmet does have a solar cell so the UV welding light likely charges something up.