What battery voltages should you see

This question arises often - either "is my battery low?" or "is it over-charging?". The answer according to a voltage monitor ($7 HR, on sale so bought 2):

Engine Off: >12.6 V "fully charged", <12.1 V "almost dead", <11.8 V "dead".

Engine Running: 13.4 to 14.8 V "normal", >14.8 V "over-charging".

The LED's show the above ideal values in my 96 Voyager. Previously, I had an Eqquis digital voltmeter ($15 Amazon), which also plugs in the cigarette lighter. As I recall, it showed 12.6 V engine off, 14.3 V engine running. Had no instructions on what is proper.

The HF one appears a bit strange since when your car is "normal" some green, yellow, and red LED's are all lit. Best to plug it in an outlet that is only powered from the key, so it won't run down your battery overnight. Since most don't have that in an A-body, maybe plug in only for diagnostics. I like a monitor on trips so I don't get surprised at a rest stop or some podunk town with no stores. I should give one to my boss since I measured 7.8 V across his battery before jump-starting his SUV last week. He said he suspected his battery was going south.