This is the procedure:
1) disconnect the positive terminal from the battery.
2) put a 2 amp charger on the battery for 24 hours or put a 10 amp charger on it for 5 hours.
3) let the battery sit for 12 hours after charging making sure to leave the positive terminal off.
4) get a digital volt meter and check the voltage on the battery - if it is less than 12.65 volts - replace the battery.
5) if it is 10.5-11.5 volts - you probably have a shorted or dead cell - replace the battery.
6) Do not run the car with a bad battery as it can put undue strain on the alternator.
7) If the battery results in #4 above is 12.65 volts or higher -(which I doubt) - reconnect the positive terminal and start the car. The voltage on the battery with car running should be 13.5-14.7 volts. If it is not - then you have a bad alternator or brush pack in the alternator.
Hope this takes the mystery out for you.