The battery has but one job - to start the engine. The alternator does all the rest, and charges the battery back up after a start.

The headlights are a large current draw, so if the alternator is not charging, the battery will drain fairly quickly. Your post said the failure was at night, right?

The flickering warning lights are the clue.

When the key is in Position II, before starting, the warning lights should all be on. Five of them get their ground through the alternator brushes. There is a wee bit of current flowing that route, just enough to pre-excite the alternator once the engine begins running. Without that pre-excitation, the alternator won't charge.

The warning lights come on whenever the thin red wire connected to the rear of the alternator is grounded. If they come on while running, that wire is grounding "illegally" and the alternator is not charging.

Check that wire, and look at the wire to the oil pressure sensor, too. Crumbling insulation means both wire are dmaged, probably inside the under-the-engine-front harness.

there are numerous posts on how to install a by-pass wire, both alternator and oil pressure, to eliminate the problem. Do a search.

Good Luck,

Bob

:>)