[persnickety]

There were calculators in the '90s where the display would go faint when you covered the tiny solar panel. Perhaps the battery was already drained. Quite common I would say.

[saagarjha]

I had one in the 2010s when I was going through grade school. Casio fx-260 solar; it would die in seconds if you covered the panel.

[aitchnyu]

The screen would go faint and slow when the power sources werent running at peak.