What Is Car Battery Voltage?

Car battery voltage is one of its basic technical parameters. It shows the level of its charge and can tell a lot about the state in which the cells or alternator are. How to determine the level of charge of a battery by measuring its voltage? How much is the correct voltage of the battery? What does the measurement result indicate? Discover how a simple measurement can check your car's battery voltage. You can do it yourself in just a few minutes!

Driving a car charges the battery

A car battery should charge itself when the engine is running. The alternator is responsible for charging the battery by supplying it with electricity, so there should be no discharge in a regularly used and efficient car. Malfunctions in the charging systems (alternator, rectifier, voltage regulator), malfunctions in the electrical system (current draw at a standstill) or failures of the car battery itself can be responsible for technical problems.

Knowing the right voltage, recognizing when something goes wrong, and determining what further actions to take to prolong the car battery's lifespan is essential.


What is the car battery voltage?

The correct car battery voltage when fully charged should be 12.6 - 12.8 volts and should not exceed these values. A voltage between 12.45 and 12.6 volts is usually the result of temporary undercharging, but this does not require action. It should return to normal after driving the car for a little longer.

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Is 12.3 volts OK car battery?

If the car battery is less than 12.4 volts when it's not being used, it means it's about 60% charged. If the car has had a long layover, this is a natural discharge of the battery, and you just need to recharge it. 

A charging voltage of less than 12.4 volts in a car that is driven often may mean that the car battery is failing or getting worn out. The battery's capacity has already gone down by more than a third. Identifying the cause requires further diagnostics, measurements of the charging voltage, starting current or intake at rest.


Minimum battery voltage - check the battery charge level

About 12 volts is usually the minimum car battery voltage to start a gasoline engine. In the case of diesel units, even having a voltage of about 12.4 volts can cause starting problems.

Using a battery in a state of permanent undercharging (e.g., caused by an alternator failure) shortens its life and can lead to problems with starting the engine because as the charge level decreases, the value of the generated starting current, which is the most important parameter for this process, also decreases.

If the car battery voltage at rest is below 11.9 volts, this usually indicates extreme degradation and replacement with a new one is necessary. A long-term discharged battery can lead to permanent damage. This can happen in a long-term period of not using the car, then when there is a phenomenon of increased current consumption. Then the battery in the car can become completely discharged. A case of deep discharge will also be when the alternator returns current to the battery insufficiently. With a defective alternator, the level of discharge of the car battery is greater than that supplied by the alternator.


How to test a car battery with a multimeter?

With a quick check of the car battery voltage, you can easily determine its level of charge. The easiest way to do this is to use a multimeter, a device that has the option to measure various electrical quantities. In the case in question, use the voltmeter built into this tool. You can also use the voltmeter itself for this, if you have this type of device. All the following steps are useful for cars shown on last sold vehicles page. Check out how to measure voltage correctly.

The measurement should be made an hour after the car battery has stopped charging, that is, after both disconnecting the charger and driving the car. Remember to do it with the engine off. After locating the battery, close all vehicle doors and turn off all power consumers. This is important because the increased current draw from the battery will affect the reading. The best solution is to disconnect one of the battery terminals, but this is not a must.

Set the dial of the meter to measure DC voltage - it will be marked with the letter V and the symbol of two parallel lines, continuous and dashed. Set the range of the meter to the first one available above 14 volts, in some devices you can also use the automatic range measurement.

Apply the measuring tips of the meter directly to the terminals of the vehicle battery. In digital devices, the polarity of the voltmeter does not matter much. If you apply the plus of the meter to the negative terminal of the battery, the screen will show the value with a minus sign, but the measurement as to the numerical value will be correct. You can read the value of the battery voltage.


How to choose car battery?

The lifetime of a battery is limited. When it eventually wears out, the service shop will often offer to sell you a new one on the spot, without the need to look for a suitable unit on your own. If the workshop does not offer such a service, you will usually find one at the nearest battery store without any problems.

Sometimes the installation service is included in the price of the battery. Both in the store and in the workshop, you will not have to pay a deposit for returning the old and inoperative one for recycling. This is a convenient and inexpensive solution, and with the assurance that the battery will be disposed of properly, you will be doing a service to the environment.

If you want to buy and replace the battery yourself, check the parameters recommended by the manufacturer. Wear and tear could also be the result of installing a battery that is not suitable for your car. Also pay attention to the dimensions and placement of the battery's terminals. If the poles have the opposite polarity, you will not connect it to the car.

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