Nissan Repair: 1993 Nissan Sentra alternator, nissan sentra, dead batteries

Question
For a year, I had problems with dead batteries.  Had to replace two in that time frame.  Took the car to two different shops and they could not find problem with alternator and thought I had defective battery.
When the third battery went in months, I took the car to a third place.  they found a problem with the alternator and fixed it.  It was pricey.  Now a year later, my car is parked out front with a dead battery again.  The car has 220,000 miles on it. But  other than this recurring battery nightmare, no other problems.  Help!! What do you think this could be and should i get it repaired again?  

Answer
I bet they put a cheap alternator on the car and it is going out and taking the battery with it.  If you have an Autozone or equivalent parts store in your area they will check the output of your battery and alternator for free.  The come out to the parking lot with their machine and validate the problem and you get to watch the results.  I would think it was the alternator as most rebuilds that are not purchased through Nissan last about a year.  Do it soon or the lack of voltage coming out of the alternator will take the new battery out too...