Car Battery Voltage

One of the most important parts of any car is the battery and by knowing the correct car battery voltage, you can easily check that it is charged and in good condition. It can confuse many people, as they believe that a normal car battery would be charged when it is at 12 volts and empty when it is at 0 volts. This is not true and in fact, there is a very small range around 12 volts where the car battery voltage moves from fully charged to fully discharged.

Popular Batteries and Voltages

These voltages are readings that are for standard lead-acid batteries and low maintenance batteries that are inexpensive and common in older vehicles.

Measured Voltage State Of Charge
12.65 Volts Completely charged
12.24 Volts Partially charged
11.89 Volts Fully discharged

These voltages apply to the more expensive and modern maintenance free, glass mat and gel batteries. These are found on most modern vehicles and are available as replacements for older models.

Measured Voltage State Of Charge
12.77 Volts Completely charged
12.29 Volts Partially charged
11.75 Volts Fully discharged

It is important to know the normal car battery voltage so that you can do, a simple car battery voltage test and be able to see if your battery has a charging problem. One point to consider is that temperature can have a dramatic effect on voltage with cooler temperature dropping voltage and the figures shown above are applicable to 70 degrees Fahrenheit. There are many factors that will affect the life of your battery, so the only real way to see if the battery is good still is to test it.

Car Battery Voltage Testing Equipment

There are a range of devices that you can use if you want to test your car battery voltage or state of charge. If you have a multi-meter then it is quick and simple to attach the leads to the positive and negative terminals of the battery. Your battery should be at or very close to the fully charged voltages that we have listed for common battery types. If there is a reading below the normal car battery voltage level then the battery or charging system may need to be checked.

A more complete car battery voltage test device is called load testers. These allow you to test the battery under load and give more information about the health of the battery. This is done by putting the battery under stress and then measuring how much the voltage drops during the process. This test should be done yearly before the cooler winter months that will put the most strain on the battery.

In older style batteries, a specific gravity test can be used to show the state of charge. It was the most common way to test batteries before electronic test equipment became common outside of garages. The device is only useable in batteries that are not sealed and allow you to access the acid solution inside the battery. The tester looks like a giant eyedropper and you simply suck in enough liquid to raise the measuring float. The float has a green and red area and you can quickly see if the battery is charged.