Testing a car battery with a multimeter | Expert Opinion 2024

It can be pretty frustrating if your car doesn’t start for some reason. This situation can be caused by many factors, including faulty alternators and car starters. But usually, the culprit is the car battery. Many car owners would check the car battery first if they experience ignition problems.

How to Test Your Car Battery’s Charge Using a Multimeter?

This article will discuss 5 extremely easy-to-follow steps for testing a car battery with a multimeter; however, we also offer other control methods if you don’t have a multimeter. Follow this article, Testing a car battery with a multimeter to the end to master these steps, and you won’t be bothered by an empty battery. 

The importance Testing a car battery with a multimeter?

Car batteries are essential when starting your vehicle. Testing a car battery with a multimeter If it fails, you will not start the car and other electrical components. Most drivers will perform a car’s battery voltage test only when the battery begins to show wear signs. However, it is best to test your battery regularly. It would be best if you had your battery tested at least twice a year to reduce the chance of malfunction. 

There are several methods for taxing a car battery. The most famous technique is checking the battery with a multimeter. The digital multimeter can be easily purchased online or at a nearby car store. If you don’t have a multimeter at home, there are other charging methods with other tools for Testing a car battery with a multimeter. 

You can perform a visual inspection of the battery holder and cables to diagnose potential battery problems. Even if the battery is brand new, the battery may still function properly if the case is broken. Ultimately the damage will render the battery unusable.

If you notice any swelling in the battery, It could mean that the battery is overcharged and the acid has been converted to gas. When this happens, you should also check your charging system.

Simple Steps in Testing a car battery with a multimeter 2024

1. Check for corrosion and dirt

Before testing the load, locate the car battery. Car batteries are probably located under the engine compartment or somewhere in the trunk. Check both negative and positive connections for corrosion. This greenish-yellow structure can disturb the multimeter values. 

You can quickly solve this problem by using a piece of sandpaper to remove the corrosion. Clean the terminals until everything is good and free of construction. It would help if you also cleaned the inside of the battery post cables to get a more accurate reading. Do not forget to use gloves as it is difficult to get the corrosion or acid from the car battery on the skin.

2. Prepare the multimeter

Using a multimeter can be a bit daunting for people who haven’t used the tool before. However, the multimeter is easy to use and one of the cheapest tools to check your battery charge. First, you need to set your multimeter to Ohm and set it to 15 volts or higher. Most multimeters support 20 volts, which is usually closest to 15 volts. 

Before using the multimeter, turn the headlights for two minutes. Doing so will remove any surface charge from the battery. Turn off the headlights after two minutes and continue using the multimeter.

3. Touch the battery terminal with the appropriate meter probe

To use the multimeter, you need to touch the probe to the correct terminal. The red search is for the positive pole, usually covered with a red cap or marked with the “+” symbol. Place the black probe on the negative bar, traditionally labeled “-” or covered with a black protective cap.

The digital display must show a positive number (e.g., 12.6). If there is a negative sign when reading (e.g., 12.6), you have placed the wrong terminals’ probes. 

If the multimeter reading is approximately 12.6 V, the battery is in good condition. When it drops 12.2V, the battery is 50% charged, and below that, the battery is empty. This measurement is the quiescent voltage. To properly measure the battery charge, you must test on the Cold Cranking Amps or the CCA.

4. Apply a light load to the battery

To check for the battery’s cold start amps, provide a light load while the probes are attached. This is accomplished by only starting the car and observing the reading changes. It is preferable to have an assistant who will start the vehicle to view the changes yourself.

5. Analyze the result

After starting the car, the reading should drop for a while but begin to rise again. Normally the measurement goes up to 14V, and this is because the alternator charges the battery. After that, you need to turn off the vehicle and wait for the reading changes. 

If the value dropped to 10 V or more after turning off your car, the battery is still good. However, if the value drops below 10V, the battery may show signs of wear and will likely break quickly. If the value is less than 5V, consider replacing a  battery.  

3 Ways to check the battery without a multimeter?

 It can also be used to control the alternator, which is the part that keeps the battery charged. If you don’t have a multimeter at home, you can use one of the methods below, depending on your circumstances.

Via hydrometer

The hydrometer test, also known as the electrolyte gravity test, is another way to perform a load test in a car battery. A hydrometer with a built-in thermometer is preferred when testing the load.

Use acid-resistant gloves before performing this test. Also, make sure not to use a metal thermometer as it could cause an explosion. First, you need to remove the cover on the top of the battery. Carefully dip the hydrometer needle into the first cell and record the reading.

Do this with all battery cells and compare the result with the specific gravity of the manufacturer’s electrolyte. You will find this in the package. If the value is between 1,265 and 1,299, the battery is charging. If the value drops below 1,265, the battery is insufficiently charged. If the value is between 1,155 and 1,120, replace the battery.

Via battery status indicator

The majority of new batteries have a pre-installed health battery indicator. This is usually the round glass shade that can be seen in one of the corners.

If the battery status indicator is red, the battery is low. If the battery color is already transparent or no color, the battery is already empty, and you need to replace it with a newer battery. This method does not apply if you have an older battery.

Via Power Probe

Power Probe testing is an easier way to test a car battery. Some drivers prefer this because of the ease of use.

First, you need to make sure the car battery is fully charged. This step can take up to half a day or more if you choose slow charging. After the charging phase, plug it back in and turn on the headlights for two minutes. This will remove the surface charge. Turn off the headlights after two minutes.

Connect the Power Probe connector to the positive pole and note the voltage. If you have a Power Probe hook, connect the hook to the battery and record the reading. The battery is still good if the reading after charging is 12.6 V or higher at 80 ° F. If the value is less than 12.4 V at 80 ° F, consider replacing your battery.

By checking the performance of electrical components

If you don’t currently have diagnostic tools, checking the performance of your electrical components is the best way. One way to do this is to start your car and turn on the headlights.

You must then run the engine and observe the lights. If the lights get dim, the battery is not charged or has almost no power. A brighter light, when turned up, means the alternator may have a problem. The alternator may not be able to produce enough power to keep the battery charged. If the light does not change after the engine starts, your battery is probably doing fine.

Via Dashboard Battery Light

 If you put your key in the ignition and the battery runs in the run position, you should see a battery sign on the car dashboard. Start the car and observe the battery indicator. If the battery symbol disappeared after the engine started, your battery is still in good condition.

Car battery vs. alternator vs. car starter

All the above tests indicate the operation of a battery. However, your car and other electrical components are still not working properly. In this case, you may need to test your alternator. 

A car battery may be in good health, but the battery will not charge properly if the alternator is defective. If your alternator leaves a growling sound after it goes out, chances are it’s already bad. Another sign is when your car engine fails after it starts. The alternator also emits a burning rubber odor if it overheats.

How to test the alternator when the car does not start?

You can reuse the multimeter for this. You must run the engine to test the battery. Take extra care and watch the moving parts to avoid accidents. Set the multimeter to 20DC Volts.  Start the engine and view the reading while the engine is running. The reading should be between 14.2 V and 14.7 V. If the number exceeds 14.7 V, the alternator will overcharge the battery. 

 However, if the value is below 14.2 V, your battery is insufficiently charged, and you may experience a problem when using accessories and headlights. Turn on the car’s electrical components such as the headlights, radio, or computer to further test your alternator. 

If the car battery and alternator are working fine, the problem is probably in the car starter itself. A clicking sound when you turn the key is a sign of a faulty car starter. In this case, you may need to seek professional help to troubleshoot your car.

Final thought on testing a car battery with a multimeter

Car batteries have an average life of three to five years. Only a fraction of this number can reach four years. The typical warranty coverage of car batteries is also about four years. 

To know whether the car battery is already at the end of its life, regular testing must be carried out at least twice a year. A multimeter is an excellent diagnostic tool that helps measure the voltage of the car battery. This tool is a must in every car owner’s toolbox. It can test both the alternator and battery for problems making car diagnostics a lot easier. 

Modern batteries have useful indicators for testing a car’s battery capacity when no tools are available. Testing a car battery with a multimeter Some tools such as the voltmeter and hydrometer can check your battery. 

Newer car models use battery indicators, which is very useful for new car owners who are just starting to learn about their cars. We hope to simplify your steps with our guide on testing a car battery with a multimeter.

 Master these steps so you won’t be surprised again by a faulty battery.