Testing a car battery with a multimeter

 As a car owner, it is helpful if you know how to test a battery. There are many batteries today that no longer require periodic maintenance. This does not mean that they have an infinite life. Therefore, everyone still needs to know how to check the condition of a battery in their car. You can do this by using a multimeter.

Testing the battery with a Multimeter

Some of the world's best battery testers are digital multimeters. They work best on so-called maintenance-free batteries. This type of battery has no caps that can be opened to gain access to the different chambers or 'cells' of the battery. They are sealed units, which prevent electrolytes from leaking onto the surface of the battery.

Multimeters measure voltage, resistance and electric current in an electrical device. Because batteries have an electrical charge, a digital multimeter can measure the current charge status of the battery. This will give you an idea of whether your car's battery is charged enough to work properly. If you have a maintenance-free battery, then a multimeter is suitable for your situation.

How does a multimeter work?

A multimeter works simply. However, before you start testing the battery, it is best to become familiar with the functions of the digital multimeter. There are small differences per manufacturer, but they all contain a mechanism to measure voltage and maximum voltage. Always read the manual first, so you know how to operate it.

The multimeter is supplied with two electrical connectors with metal probes. The wires come in two colours: black and red. The black coloured wire is negative, while the red coloured wire is positive. It is very important not to put them on the wrong pole. You don't want to connect metal probes to the wrong battery terminal.
If you are going to test the battery with a digital multimeter, set the device to DC or Direct Current. Make sure you set it to 20 volts. A healthy battery should have a charge of about 12.6 volts. It is sufficient to set the multimeter to 20 DC volts.
Take the black metal probe and touch the tip to the negative terminal. Take the red metal probe and touch the tip to the positive battery terminal. The resting voltage of a healthy battery is about 12.6 volts. If someone can assist you, ask them to turn on the car's headlights, then you will see a drop in the voltage reading in the multimeter. It may be 12.5 volts, for example.

Low voltage in the battery

If the resting voltage of the battery is 12.3 volts, you can say that it contains about 75 per cent electrical charge. 
It is also important to remember that there is such a thing as 'parasitic loss'. There will always be some car components that use electricity, even when the engine is already switched off. The computer, digital clock, security system and other components can still use power from the battery. This can lead to a reduction in battery charge over time.

If you test the car battery with a digital multimeter and the voltage is too low, you can take the battery out of the car and charge it overnight with a battery charger. Then test it again the next morning. If it can hold the ideal charge, it is possible that a component in the car is causing the battery to run down. If the voltage remains too low, it is probably time for a new battery.

Problem with the battery terminals

There are situations where the battery itself is not the problem. Rather, it is the battery terminals. If these are corroded, loose or dirty, you will still have problems starting the engine. It is also one of the most common reasons why people think their battery is dead.
The good news is that you can use your multimeter to check for faulty battery terminals. To do this, you need to switch off your car's ignition system. The easiest way to switch off the ignition system is to remove the relay or fuse for the fuel pump. Another method is to disconnect the ignition coil. Each of these methods prevents the car engine from starting. Only do this if you are technically skilled, otherwise a mechanic is a better option.

Now take the red metal probe from the multimeter and place the tip on the positive battery terminal. Now take the black metal probe and place it on the same battery terminal. Ask someone to switch on the engine of the car. Look at the needle on the display of the multimeter. If you read more than 0.5 volts, there is a chance that the positive battery terminal is dirty or corroded.
Perform the same procedure on the negative pole connection. You must first touch it with the black metal probe before using the red metal probe. Let your assistant start the engine. If you see a voltage reading higher than 0.5 volts, there is a problem with your battery terminals. Again, the best solution is a new battery.

FAQ multimeters

Below we have listed the most frequently asked questions about Multimeters. Do you have an additional question? Then ask it in the comment field. We will then add your question and answer to this page.

 

• What is a multimeter? A multimeter is a tool designed to diagnose problems with electrical and electronic circuits. It is used for checking voltages to verify proper operating levels.
• What does a multimeter measure? Standard multimeters measure current, resistance and voltage. More expensive models can also measure capacity and induction.
• Multimeters combine three functions. An ammeter measures current, an ohmmeter lets you determine resistance and a voltmeter measures the voltage between two points. Multimeters combine all three functions in one instrument.
• Measuring amps with a multimeter. The ampere measurement function of a multimeter is used to measure the number of electrons that pass a certain point for a given time. The units in this measurement are known as amps. Your multimeter can check how many amps, e.g. A device uses.
• Measuring ohms with a multimeter. The ohmmeter function measures electrical resistance - the opposition to an electric current - and uses units known as ohms. An electrical circuit has a resistance of zero or close to zero ohms when shorted. When a circuit is open, it has an infinite resistance and no current.
• Measuring volts with a multimeter The voltmeter function of a multimeter measures the electrical potential between two volt points and is particularly useful for checking whether a battery is low. In addition, a multimeter can measure current and voltage in two different modes: alternating current (AC) and direct current (DC). Domestic sockets almost always use alternating current. Please note that different countries have different standards.