The voltage of a good automobile battery should be around 12.6 volts. It's crucial to test the battery after it's been laying for at least an hour to determine what's known as the 'resting voltage.' If you've been driving recently (and the charging mechanism is working properly), the battery will likely produce a more significant number than the resting voltage, which could be misleading. Better yet, park the car overnight and examine the battery the following day to receive a more accurate picture of the charge state.