Doug has put us out of our (and his!) misery. I ran a test with our newest vehicle, a 2016 Ram Promaster City van.
Idling and warmed up showing 13.79 voltage at battery with multimeter, no battery dash light.
Using adjustable voltage deck mount converter with clamps on the wires (PowerMax LK) I set voltage to 14.6 and clamped on. Nothing happened, no light.
Cranked the voltage up slowly and the engine stumbled but kept running when voltage was 14.99, looked at dash and the battery light was on bright red. Disconnected charger and battery voltage back to 13.8ish but light still on.
Turned off the ignition and restarted. All normal, no red battery light
I am not sure it is ok to keep driving with the light on from over-voltage like that, seeing how mine had that engine stumble (almost died then back on full) when the voltage reached whatever it didn't like, but I have no knowledge of all that.