A typical car battery voltage when fully charged and the engine is off is around 12.6 volts. The normal voltage range for a car battery is between 12.4 to 12.7 volts. When the engine is running, the voltage can be higher due to the alternator charging the battery, usually between 13.7 and 14.7 volts12. It’s important to note that these values can vary slightly depending on the battery’s age, the temperature, and the state of charge