A car battery is designed to provide a nominal voltage of 12 volts. This is the standard voltage rating for most modern car electrical systems.
However, the actual voltage of a car battery can vary depending on its condition and operating state:
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Fully charged resting voltage: When the engine is off and the battery is fully charged, it should ideally measure around 12.6 volts. This indicates a healthy battery with sufficient power to start the car.
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Voltage during engine crank: When you start the engine, the battery experiences a temporary voltage drop due to the high current demand from the starter motor. This voltage drop is normal and usually momentary.
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Voltage while engine is running: Once the engine is running, the alternator takes over the task of supplying power to the electrical system. The voltage reading should then be slightly higher, typically in the range of 13.5 to 14.5 volts. This indicates that the alternator is properly charging the battery.
If you're concerned about your car battery voltage, you can use a voltmeter to measure it. It's a good idea to consult your car's owner's manual for specific recommendations on ideal voltage readings for your vehicle.