1999 Chevy Lumina Dashboard Voltage Light (and other lights

Electrical problem
1999 Chevy Lumina 4 cyl Two Wheel Drive 147000 miles

I am trying to determine if I have a problem with the alternator or other electrical problem or not. I've always had false problem lights show up on the dashboard, such as service engine soon. My dashboard started to go dim some months ago, and recently I replaced a dead battery with a used, less powerful one. Now, the volt light is going on, which never lit up before. The car has been starting, but how can I determine what the problem, if any, might be?

Thanks,
Al