It is the most annoying moment when your car fails to start. This is a common problem for many users which is capable of making your morning upset. When your car fails to start, a low or dead battery could be the offender. The battery equipped in your vehicle is responsible for providing the needed electricity. Fortunately, you can check the state of your car’s battery using a multimeter. In this article, we’ll see “How to Test a Car Battery with a Multimeter?”
Since you’ll be unable to start your car without a functional battery, it’s essential to assure that the battery is all good. A standard car battery usually lasts long for about 3-5 years, when bought a new one. The lifespan of a car battery depends on various factors, especially how you drive your car. If you drive harshly, drive in extreme conditions, and run a lot of electronics while driving, then you shouldn’t expect longer battery life.
Table of Contents
- What is a Multimeter?
- How to Test a Car Battery with a Multimeter?
- How to Clean a Car Battery?
What is a Multimeter?
A multimeter is an electronic measuring instrument that is a standard tool for every mechanic. They are used for measuring voltage, current, and resistance of any electrical object. The most common application of multimeters is in the automotive industry. People can use multimeters for testing the strength of a car’s battery. With sufficient skills and experience, you’ll be able to read out voltage measurements to a high level of accuracy.
A multimeter could be of two types: analog and digital. Nowadays, digital multimeters are very common because of the increase in affordability and convenience. In this article we will talk about how you can use a best multimeter at home for testing your car’s battery.
How to Test a Car Battery with a Multimeter?
As said earlier, a voltmeter is a device that can measure voltage and inform you about the battery’s status. Obviously, not everyone will own a multimeter, but if you’re willing to maintain your car, you must pick one best multimeter for home use. If you already own a multimeter in your toolkit, all you need to do is follow these straightforward steps.
If you not aware of how to user to use a multimeter you can check out here.
Step I: Some Prerequisites:
First of all, unlock your car, insert the key, and turn on the headlights. Here, wait for at least 2 minutes with the headlights being turned on. You don’t need to turn on the car, just the headlights(reason discussed below). This will do away with any surface charges present on the battery.
You’ve to make sure that you don’t test the battery immediately after riding the car. Because the battery may be holding some charge from the alternator. If you do it intentionally or mistakenly, you may receive false/inaccurate readings. That’s why we suggest you to not turn on the car.
Step II: Visually Inspect the Battery:
Open the hood/bonnet of your car and locate the battery. You can also check the owner’s manual for the same. You’ve to make sure that there isn’t any dirt or corrosion build-up on the terminals. This corrosion is usually a build-up of white or yellow crust around the metal. The positive terminal will have a red cover(with “+” sign), and the negative terminal will have a black cover(with “-” sign).
The corrosion or dust on the terminals would result in inaccurate/false voltage readings. It may be possible that corrosion itself is the reason behind the faulty battery. You can use fine-grit sandpaper or terminal brush to scrub off the coating. Don’t forget to wear gloves for avoiding any contact with harmful chemicals or acid. If the terminals don’t have any corrosion, you’re ready to bring the multimeter into the scene.
Step III: Setting Up the Multimeter:
A new user may find multimeter to be a complicated instrument because of various measurement settings. However, the basic operation of a standard multimeter is pretty simple. The car battery is prepared at this stage, and you have to set the multimeter voltage to ’20 volts’ DC. Some individuals may tell you to range between 15-20 volts, but make sure it must be above 15 volts. This would help users to get correct measurements.
In step I, we asked you to turn on the lights for 2 minutes. Another notable point is that you must turn-off the headlights at this stage. Your multimeter will show you an option to select an AC current. However, you’ve to measure only DC now, not AC.
Step IV: Use of Multimeter Probes:
Any multimeter comes with two probes: Red and Black. In this step, you’ve to touch these probes with your car’s battery’s correct terminals: meaning, the positive probe with the positive terminal, and the negative probe with the negative terminal. We’ll inform you once again; the red probe is positive while the black probe is negative.
Take a look at the digital display and observe the sign. If the screen shows a positive number (e.g., 12.6), you’ve placed the probes correctly. Else, you’ll get a negative reading (e.g., -12.6) when probes are inserted incorrectly.
Check Out: How to use a voltmeter
Step V: Check the Measurements:
After touching probes with correct terminals, you need to check the display readings. If your car’s battery is fully charged, you should expect your multimeter to display somewhere between 12.2 to 12.6 volts. This means that the battery is in good condition and ready to start the vehicle.
If your car battery is around 75%, the multimeter will display a reading of 12.45 volts. Any reading around 12.2 volts means the battery is 50% charged. However, if you find any figure below 12.2 volts, then your car’s battery is discharged. Your battery will not work in this case. The car will start again after charging or replacing the battery. You’ve to learn a simple mantra – the colder the battery means, the lower the multimeter readings.
Step VI: Measuring the Cold Cranking Amps of the Battery:
In order to check the cold cranking amps of the battery, you need to throw a light load in the battery. All these need to be done when the probes are touching the terminals. Now, ask your family member or anybody to start the ignition with the multimeter being connected. Stay ready to notice the changes very quickly.
The moment you turn on the car, you’ll witness a sudden fall in the readings of the multimeter for a quick second. However, the readings will rise and even go up to the 14-volt mark as the alternator charges the battery. Now, ask your assistant to turn off the car and wait for the readings to settle down.
Step VII: The Final Analysis:
In the previous step, we asked you to turn off the car and notice the reading. If the reading drops down to 10 volts or above, then the battery is still in good condition. However, if the reading goes below 10 volts, your battery isn’t healthy and will wear off very soon. But if the reading goes down to 5 volts, you need to replace the battery with a new one.
How to Clean a Car Battery?
BONUS! In this segment, we’ll provide you with some extra information on how to clean your car’s battery. The battery is the most crucial part of a car. So manage your time and let’s do this.
Step I: Clean the Battery Case:
Open the bonnet and locate the battery there. Now, you’ve to follow a simple procedure to clean up the battery case. Take a cup (around 8 ounces) of warm water and a little bit of baking soda. Mix them well. This basic solution will neutralize acid and easily clean up the dirt over the battery case and terminals.
Take a soft brush and dip into the solution prepared. You’ve to apply the solution across the top and side of the battery case. Make sure you wear gloves and goggles to protect yourself from harmful chemicals and battery acid. If your car comes with a maintenance-type battery (with cell caps), protect the solution from going under the caps. Wipe the solution using a cloth if you didn’t find anything getting build-up.
Step II: Clean the Battery Terminals:
Similar to step I, it’s time to remove dirt or corrosion away from the battery terminals. You’ve to use the same baking soda and warm water solution for cleaning both the terminals. You can also pour the solution into a foam cup and dip the terminals for about 2 minutes.
After doing this, take a battery-post cleaning tool and remove the corrosion (yellow build-up) from the terminals. Keep repeating this step until you find your car’s battery free of corrosion.
Step III: Clean the Battery Tray:
Another important part of your car is the battery tray. Take a look at it and make sure there is no missing part, lost screws, or any signal of corrosion. If you want to clean the tray, use the same solution for removing any dirt or corrosion. That’s all; your car battery is fine and ready to start the vehicle.
Car batteries usually last long anywhere between three to five years. Even the manufacturers provide a typical 4-year warranty on the car’s battery. To check whether the battery is working fine or not, you must check it at least twice a year. A multimeter is a fantastic instrument for electronics use that allows you to measure the voltage of your car’s battery. It can test both the battery and the alternator of your car. We’ve discussed every step comprehensively to help all our readers. We hope that our guide on How to Test a Car Battery with the Multimeter turned things easier for you.