With the car running it should have at the very least 14 volts at the battery terminals. Actually 15 volts is better and I like to see 15.5, moreso for people who are in the north and drive in the dark.

You also need to know if there is an abnormal load draining the battery. This is shown by taking off one battery terminal and connecting a taillight bulb, or other 12 volt bulb to connect it.