Yup. Lead acid are fully charged below 12.6 Volts and the range for engine running is 13.7 to 14.7. Anything higher then 14.7 volts are a fully charged battery is actually cooking the cells.

The bummer is that 12.4 is when a car battery is dead. Below that you are sulfating off your conductive plates. so 12v is not a good reading at all.

When it gets cold in the winter. I sometimes hook a 2 amp charge over night on the vehicles I am driving. That way if they were down a little the charge will bring them back up to full state.

People do not fully understand that the alternators on most modern cars are only for maintaining a charge. If you accidentally drain one down. You really should charge up up for 12 or 24 hours a a low amp charge. :-)