What is what voltage is a car battery?

A car battery is typically a 12-volt battery. While referred to as "12-volt," the nominal voltage is closer to 12.6 volts when fully charged. During starting, the voltage can drop below 10 volts, but it should quickly return to a higher voltage when the engine is running and the charging system is active. The charging system, regulated by the alternator, typically maintains a voltage between 13.5 and 14.5 volts to charge the battery and power the car's electrical components.