Crap like this is why I don’t ferry airplanes at night.
Crap like this and my experience below are why I don't so SE night XC's, just local night flying where I know the terrain and airports.
If you lose the alternator you have about 20 to 30 minutes before the battery goes dead. If you lose the alternator you have 20 to 30 minutes land at the first available lighted airport.
Correct, and you get that 20-30 only if the battery is in top shape. The older battery, the earlier lights go out...
That’s assuming you notice you lost the alternator....
Well, for me it went like this. Ammeter needle swings wildly back and forth several times, then shows severe discharge. 30 seconds later, get HIGHLOWVOLTS on the annunciator panel. Call center, apprise them of the situation, and then divert. Elbow your partner, who is sleeping soundly in the right seat, and have him turn off unnecessary avionics and then start pulling unneeded breakers to shed load.
Once in the diversion airport environment, note that you still have zots and put the gear down, so you don't have to start the lawnmower 50 times. Lastly, in a fit of brilliance, click the mic 7 times to get the PCL up. On downwind, watch as everything still lit on the panel flickers twice, and then darkness. On final, be thankful you got the PCL up. After landing, be thankful the weather was VFR. Call a cab, get a hotel, then get a beer. Or several.
Next day, CAVU, beautiful morning, no mechanic on field. Actually a pretty deserted field. Find battery had recovered enough overnight to run the boost pump and start the engine. Pretend you're a NORDO cub, avoid all airspace where you have to squawk/talk, and fly peg leg to facility with mechanic.
Vow not to fly SE XC at night again.