How Many Volts Is A Car Battery & How To Test With Multimeter?

car battery voltage test

The battery is one of the most important parts of the vehicle, which helps in starting the engine and also provides DC power supply to all the electrically driven parts of the vehicle. Such as vehicle headlights and taillights, sensors, radios, wiper motors, and air blower motors.

In this post, we will discuss the battery voltage in detail. For example, what is battery voltage, how many volts is a car battery, and how do you test it?

What is Car Battery Voltage?

Car battery voltage refers to how much DC electrical power is stored in the car battery, which enables the battery to successfully operate various electrically driven components of the car. A fully charged 12V car battery has a voltage of 12.6 to 12.8V with the engine off and 13.5 to 14.7V with the engine running. Because various components of vehicles require a certain voltage to function,.

Accordingly, the car battery provides sufficient voltage to the vehicle’s electrical components. When the voltage of a car battery is low, the vehicle’s electrical components cannot function properly. Therefore, to keep the voltage of the car battery stable, the alternator is continuously charged while the engine is running.

How Many Volts Is A Car Battery?

  • Car Battery Voltage With Engine Off : 12.6V To 12.8V
  • Car Battery Voltage With Engine Started : 13.5V To 14.7V

A healthy 12V car battery has a voltage range of 12.6 Volts to 12.8 Volts with the engine off. But when the engine is running, the car battery voltage ranges from 13.5 volts to 14.7 volts when the alternator is chargingHowever, the car battery voltage also depends on the output voltage of the alternator’s regulator when the engine is started.

Causes Of Drop Car Battery Voltage

Common causes of car battery voltage drop include continuous use without adequate recharge, battery age, electrical system faults, bad alternators, extreme temperatures, and corrosion on the terminals.

1. Bad Alternator

The main reason for the drop in battery voltage is a bad alternator. because the alternator continuously charges the battery while the engine is running. Due to this, the voltage of the battery remains constant. But a bad alternator is unable to charge the battery.

2. Loose or Corroded Connections

If your vehicle’s battery terminal connections are loose or corroded. Then the charging supply from the alternator is interrupted, due to which the flow of electricity in the battery is not sufficient. The car battery is unable to be fully charged.

3. Battery Age

The condition of the battery and older batteries make them unable to store voltage for an extended period of time. That’s why the voltage of the battery starts to drop quickly. Sometimes a damaged car battery won’t charge through the alternator.

4. Bad Voltage Regulator

The alternator’s regulator controls the output of the supply going to the battery. But due to a bad alternator regulator, a sufficient charging supply is not reaching the battery. Due to this, the voltage of the car battery starts to drop.

5. Extreme Cold or Hot Temperatures

Often, extreme cold temperatures can result in a significant drop in vehicle battery voltage. Because starting the engine in extremely cold temperatures by the battery consumes more energy from the battery. Due to this, a drop in car battery voltage can also be seen.

Symptoms Of Drop Car Battery Voltage

There can be several symptoms of a drop in car battery voltage. By identifying the cause, you can get rid of the problem of a drop in battery voltage.

1. Car Engine Starting Problem

You will find it difficult to start the car engine due to the drop in voltage of the car battery. because the starter motor will not get enough voltage from the battery to turn the engine at full power. Due to this, it will be difficult to start the engine.

2. Dim Headlights

A drop in battery voltage may cause your vehicle’s headlights and taillights to dim or not turn on. Because of the drop in battery voltage, there will not be enough power supply to turn on the headlights and tail lights.

3. Flickering Battery Light in Dashboard

Often, during a drop in vehicle battery voltage or a failure of the charging system, you may see the battery light in the vehicle’s cluster meter illuminate or flicker.

4. Strange Noise From Alternator

Strange noises coming from the alternator can also cause a drop in battery voltage. because a bad alternator produces more strange noises, which could indicate a failing vehicle battery charging system.

How To Test A Battery With A Multimeter

First, you can test the battery voltage with the engine off. Set the multimeter to DC volts. With the engine off, a fully charged 12V battery should have a voltage of 12.6 to 12.8V, and with the engine running, the multimeter should read 13.5 to 14.7V.

  • Turn off the car engine and turn off all battery-operated devices.
  • Connect the red lead of the multimeter to the positive terminal of the battery, and connect the black wire to the negative terminal of the battery.
  • Now the multimeter should show a reading of 12.6V to 12.8V for a fully charged battery with the engine off.
  • Now, start the engine.
  • The multimeter should show a reading of 13.5 V to 14.7 V when the engine is running to check for alternator charging.
  • You can also use a battery gravity tester to test the voltage of the battery. but you have to use it carefully.
  • You can also do voltage testing of your vehicle’s battery with a load tester. You must follow the manufacturer’s instructions for using a load tester.


Q. Is 11.9V enough to start a car?

Yes, the car can be started even if the battery voltage is 11.9 volts. But keep in mind that a healthy car battery should be between 12.4 and 12.6 volts when the engine is off. if there is a drop in the voltage of your car. So it’s a matter of checking the battery and charging system.

Q. Will the car battery recharge itself overnight?

No, if the car battery is completely dead. Then the alternator is unable to charge the car battery. In this case, you will have to resort to an external source for battery charging. e.g., an AC input battery charger

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