How To Test A Car Battery With A Multimeter

how to test your car battery
It’s important to test your car battery frequently.

The car’s battery is one of the most vulnerable items. It can drain very quickly and can be very expensive to replace.

Moreover, a weakening car battery can give to rise to many problems such as delayed ignition, dim lights, etc.

While there are many ways to check the status of a car’s battery, one of the best options is to use a multimeter.

You can also check the battery’s status with the help of a battery tester or an OBD scanner that offers battery testing feature. However, if you want to keep it old school then here’s how to test a car battery with a multimeter:

Note: A healthy battery will show a voltage of 12.6 volts on the multimeter.

Preparation Before Testing Your Car’s Battery

Before you test your battery, make sure you are wearing gloves so that your hands don’t get messy.

Avoid wearing anything made up of metal, including rings and chains. They can cause you to get injured.

Make sure that your body, especially hands, is completely dry. Also, ensure the surrounding is dry as well, especially the ground.

Do not test the battery if it’s too hot. Allow it to cool before testing it out.

How To Test A Car Battery with a Multimeter: Step By Step Guide

test a car battery
Check a car battery.
Credit: spangdahlem.af.mil

Here are three simple steps to perform a car battery voltage test:

Step#1 – Locate The Battery

The battery is kept in the engine bay at the side of the engine. Therefore, you need to open the hood to get access to it.

Once you find the battery, remove its cover. In some modern cars, there’s a plastic wrap on the battery for protection. It can come out with a little pull. However, in some cases, there may be screws. Remove ‘em and you’ll be able to access the battery.

After removing the cover, you’ll find two terminals on the battery: a positive (+ve) terminal and a negative terminal (-ve). The +ve terminal typically has a red cover that you will have to lift off.

Step#2 – Attaching The Multimeter Probes

Once you can access the terminals, it is time to make a connection. Take the red probe and attach it to the positive terminal, and black probe to the negative.

If you do it wrong, the multimeter will show a voltage of -12.6 rather than 12.6. If it does so, inter-swap the probes.

Step#3 – Checking The Volts

As you attach the probes, the multimeter will display a reading. If it’s 12.6 volts then it means the battery is fully charged.

Volts below 12.6 and 12.2v imply that the battery is half charged.

Voltage measuring below 12.2v means that the battery is discharged.

This is how to test a car battery and see if it is charged or not. If it shows volts below 12.6v then pull it out and charge it with a battery charger or take it to a professional.

Car Battery Voltage Chart

12V Battery VoltageVolts Per CellCharge
12.72.12100%
12.52.0890%
12.422.0780%
12.322.0570%
12.22.0360%
12.062.0150%
11.91.9840%
11.791.9630%
11.581.9320%
11.311.8910%
10.51.750%

How To Tell If Your Car Battery Is Bad?

test a car battery
A car battery.
Credit: commons.wikimedia.org

There are many warning signs that will tell you if there’s something wrong with your car’s battery:

Poor Engine Crank

When you turn the key to start the ignition, it is the battery that ignites the engine. However, if the battery has weakened, drained or lost the charge, it will produce a lazy and slow engine crank.

On the other hand, a healthy battery will turn the engine on in one go and will only produce a rapid clicking sound.

Warning Light On The Dashboard

Moderns cars have a battery status icon on the dashboard that lights up when the battery is weak. It can help you judge the status of the battery.

However, it’s not necessary that your battery must have gone bad if the battery light is on, there is a possibility that there’s a problem in the connection or some electrical component.

Expanded Battery Case

Test a car battery
A battery is extremely important to the car.
Credit: commons.wikimedia.org

A battery works by triggering a chemical reaction in its box. Sometimes, outside elements such as heat or cold, a lack of charge can cause the walls of the battery to expand.

We see this in TV remotes as well. When we do not use the remote for a long time, the battery often gets swollen.

This happens because the battery discharges due to extreme cold or hot. Same is the case with a car battery.

Old Battery

The lifespan of a battery is 5-6 years. If it has lived its age and is reeking a strange smell then the battery has gone bad and needs to be replaced.

The Conclusion

It is important to keep the battery in good shape. When you keep your battery well maintained, it will run smooth, longer and will provide enough juice to power all electrical components efficiently.

It is a good choice to check your battery’s status with a multimeter. The process is very easy and only takes a few seconds.

Read more: Best Battery Testers Review and Comparison 2019

Tim MillerFounderOBD Advisor

I’m Tim Miller from Denver, Colorado. I’m the founder of obdadvisor.com, an automotive blog about "Diagnostic Tools and Auto Repair". My fan page is facebook.com/autozikcom. I've been working as an automotive mechanic and blogger for over 10 years writing articles to share my experiences and expertise.

Web: https://www.obdadvisor.comEmail: [email protected]
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