1990 80q battery problem

[Jason]

Alright, I replaced the alternator in my 80q about a week ago.  Along with
it, I put in a new battery and battery cables.  Car ran fine for three days
and then mysteriously the battery dies overnight.  So I tried two other
batteries for the next two nights.  Same problem.  I start the car with a
full battery one day and then 24 hours later the battery is dead.  Lights
are off, radio is off, doors are closed, trunk closed, etc.  Anyone have any
idea why this is happening.....?