Battery or Alternator or Something Else?

Hi everybody. I have a 1992 Olds Cutlass Ciera 3.3. Today the wife was driving around and everything was fine until this afternoon. She had parked in front of the house(luckily). She went out to start it and battery was dead. I thought, maybe alternator. So I pulled the alternator and brought it to NAPA. They tested it and said it looked fine,cranking 14+. O.K., I put the alternator back and pulled the battery.A Diehard Gold, which just hit 5 years old. I thought maybe I should have tried the battery first, oh well. Brought it up to Sears, and I bought a new one and it works fine. I then found the old receipt for the original battery, 3 year warranty and 100 month pro-rated. So back up to Sears to get a couple of bucks back. Dealt with the manager, who had a little attitude, but not too bad. He said he would have to check it on "the machine", some kind of fast charging unit that takes about a half hour and tells you whether the battery is good. It gives a readout of Cold Cranking Amps. After a while he said he would still give me a refund, but the battery looked good. When the half hour was up, he called me in and showed me that the battery was fine, rated close to (800 cca). The battery is only rated for (700cca) though. So my question is : Is that machine a lot of bull? Cranking up a 5 year old battery in a half hour to (100 cca) above what it is supposed to put out. I know NAPA has told me that you can't always go by their machine for alternators, but I've tested 4 or 5 before on their machine for other cars and when their not putting out, their dead. This alternator was hitting 14/15. Some other guy said something about maybe a "parasitic load" in the wiring. He lost me right there. Car is working fine at the moment. Any ideas?
Should I replace the alternator to be safe? Should I believe Sears Dude? Or should I look somewhere else. Or should I relax, have a cold beer and just see what happens? Thanks in advance to everyone. I'm gonna have that beer anyway. Take care. - JJ

Relax and have one on me! Your alternator is fine so don't worry. If the battery was 5 years old then it was due to be replaced anyway. The machine they are using is obviously overcharging the batteries they put in so that they can get around the warranty. My question is did he actually load test it or did he just check the voltage?

The parasitic load is the constant draw on the battery from such things as the computer and radio that require a small amount of voltage to maintain memory. A lot of times a battery will drain due to this load especially if the car sits for a few days or the battery is getting weak.

Yesh i got a system in my car 2 12inch kenwood and an 800 watt amp with 2 fans on it and my batt will drain in like 2 days on me if i do not start the car so i have seen it happen.

Also, may want to check voltage readings at the battery and alternator to see if they match(with engine running). Just to see if your wiring between the two is in good condition.

Thanks everybody, car is running fine. Appreciate all the help. - JJ