Charging system question

Hello people,

I'm still dealing with a couple of leaks (another post), but the reason for this post is the following:

I changed my '94 TS battery around March or so with an Energizer 700Ah from Sam's. Last week I got home and forgot to move the ignition switch from "acc" to "off" after waiting for a song to finish. Two days later I went to use the car but the battery had flatlined.

I called AAA and they had a hard time jumpstarting the van. We had to leave the battery charging for a few minutes and then crank the engine (while still connected to the cables). I drove for a few minutes and left the car idling for ~10 minutes to let the battery charge a bit more, but obviously this wasn't enough since the following day the van didn't start once again.

So I bought a charger that should shut itself down when the battery reached 14.4 volts and left it overnight. Next morning the charger was still running, and ultimately I had to leave this thing charging for a whole day or so. The battery never reached the 14.4 volts, but the charger stopped at 13.6V

Today I took the car to Sams to see if the battery was bad. The guy connected the tester and it said the battery was producing 580Ah, that it was "Ok" (I'd rather say it was "acceptable") and that just needed to be charged (and that the problem was most probably the charging system).

So, my questions are:
- Is it normal for a battery to get completely drained by a stock radio/cassette in two days?
- Should the car have charged somewhat in ~20-30 minutes, enough to start the car the following day?
- Is it normal for a 6 month old battery to be 120Ah below it's rated capacity?
- Is it possible there's a problem with the charging system, even if after starting the car the volts gauge go almost to 15V, and goes down slowly in about 20 minutes to settle right above 13V?

I believe the behavior of the gauge means the charging system is Ok, and that the battery is failing. Am I right?

(Sorry for the length of the post!)

Is it normal for a battery to get completely drained by a stock radio/cassette in two days? Definitely yes
- Should the car have charged somewhat in ~20-30 minutes, enough to start the car the following day? I woiuld hjave expected it to start again right away....and probably the next day....but it ispossible it might ask for more charge. Not conclusive yet.
- Is it normal for a 6 month old battery to be 120Ah below it's rated capacity?
Largely depends on the test method. Pulling 700 amps from a battery requires a very good contact and some expeditive test can bring less than expected. Not conclusive yet.
- Is it possible there's a problem with the charging system, even if after starting the car the volts gauge go almost to 15V, and goes down slowly in about 20 minutes to settle right above 13V?
See if the charging voltage changes when you turn accessories ON, like headlights, heater blower....Failed alternator diodes or regulator can deliver correct voltage at low load but will drop if more current is required.

I believe the behaviour of the gauge means the charging system is Ok, and that the battery is failing. Am I right? Possibly...Yes, the battery is rather new . Turn key on, and see what voltage you get..then add a few accessories...of just try starting for a second wwithout actually starting the engine then look for voltage again, in case it drops suddenly. The test is to look for a shorted cell...which arrives almost normally for a 5-6 year old battery, but unexpected for a 6 months battery though. The battery might show 12v plus for a second or so, but drop suddenly to 10V after a short period of time. The fact you charged it with an external charger and it failed, all together with other facts above, lean towards a failed battery indeed.

Alternator failure is common and original delco parts are POS. I changed my diode bridge once (used Bosch replacement) , then the built in regulator a year later.

ahhh...do not bypass the possibility of poor battery cable contact.....this is very insidious, but check simple things first....

Start van and check voltage at output stud on rear of alternator, and compare to voltage at battery terminals, should be 0.1, maybe 0.2 volt max difference..if greater, then wiring is corroded or loose. Check ground terminals, and especially the remote battery stud located next to master cylinder, they have been known to loosen up and cause all kinds of electrical problems. Clean and tighten all positive and negavtive connections
Jeff