How to Test a Car Battery?

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How to Test a Car Battery? Different Ways of Testing a Car Battery with Photos

In this article, we’ll provide detailed information on why it’s necessary to test a car battery, how often you need to do it and how to do it.

Below you’ll find the contents of the article. You can click on the chapter and read the information that you’re interested in the most.

1. Why Is It Important to Test a Car Battery?

A car battery is a very important component of your car. One of its main functions is to provide current when you’re starting the engine of your car. Besides, a car battery provides current to a number of the devices in your car that need it when the engine is turned off. For example, the light inside your car, vehicle audio, the vehicle horn and other devices in your car. When your car is parked, its car battery is responsible for the work of the warning system. While you’re driving your car, in case the electric generator can’t cope with the load, it’s the car battery that ensures everything is functioning properly. The in vehicle network can work properly only under the condition that the level of a car battery’s charge is normal.

how to test a car battery

That’s why it’s so important to regularly check the level of a car battery’s charge and, if it’s necessary, charge it on time or replace it with a new car battery.

2. What Is the Normal Level of a Car Battery Charge?

One of the main parameters showing the state of your car battery is the voltage. If the owner of a car knows the rate of his/her car battery voltage, he/she can easily define the car battery’s level of charge and its state.

The rate of voltage helps to define the normal level of a car battery’s charge. That’s why a car owner should know what the standard rate of a car battery voltage is.

normal level test car battery

The standard rate of voltage for a charged car battery amounts to 12,6 – 12,8 V. If the rate is lower, it means that your car battery is discharged.

You’ll find a table below showing the percent of a car battery’s charge level and corresponding car battery voltage rates. Pay attention to the fact that the voltage rates provided refer to the situation when there is no load on a car battery. In other words, the voltage rates provided refer to the situation when the engine of a car is turned off.

a table the percent of a car battery’s charge level and voltage

Many car manufacturers don’t recommend car owners using a car battery the voltage rate of which is lower than 12 V because it can lead to a shortened service life of the car battery itself. It’s better to charge your car battery on time in order to prevent its total discharge.

The voltage rate of a car battery may amount to 10,8 V. In this situation, a car battery is considered to be totally discharged. If you let your car battery get totally discharged several times, it will fail to function properly and you’ll need to replace it.

3. How to Test a Car Battery with a Multimeter or Voltmeter When the Engine Is Turned Off?

There are several ways of measuring the voltage rate of your car battery. The easiest way is the one where you have to use either a multimeter or voltmeter. Multimeter is a special tool used for measuring the rate of voltage. If you don’t have it, you can borrow it from one of your friends or buy at a store. It’s not expensive. However, you’d better buy a digital multimeter since it’s more convenient to use.

multimetr to test car battery

It’s very easy to use a multimeter. It’s necessary to connect the red (positive) thin gage (output) of the multimeter to the positive car battery terminal and the black (negative) thin gage to the negative car battery terminal.

Testing a car battery using a multimeter when the engine of your car is turned off.

When testing a car battery while the engine of a car is turned off, we recommend you following a simple rule: it’s better to test a car battery not tight after you turned the engine off. You’d better wait for several hours or test your car battery not long before you’re going to drive your car. The thing is that the voltage rate will still be high right after you turn the engine off. Consequently, the result you get may be incorrect.

Well, let’s get to the procedure itself. You need to connect the thin gages of the multimeter to the car battery terminals. The negative one is to be connected to the negative battery terminal while the positive one is to be connected to the positive battery terminal. You need to wait for several seconds and then compare the result you get with the figures provided in the table above.

testing car battery

The standard voltage rate of a car battery when the engine is turned off amounts to 12,6 – 12,8 V.

If the voltage rate is lower than 11,8 – 12,0 V, it means that your car battery is discharged. Consequently, you may fail to start the engine of your car.

The level of a car battery charge shows you how well a car battery can keep its voltage rate for several days. If your car battery is completely charged, the voltage rate won’t fall down significantly even when you don’t use your car for several weeks.

If the situation is quite the opposite and your car battery is discharged, the voltage rate will be falling down very fast. It means that the battery won’t keep its charge.

You can find information on alternative ways of checking the level of a car battery charge using a multimeter in the following article: How to Know When a Car Battery is Charged

4. How to Test a Car Battery Using Battery Load Tester?

The way of testing a car battery described above is a very easy way. However, the results you get are quite approximate. They are not exact. The best way to test your car battery charge level and check whether it’s functioning well is the way where you have to use a Battery Load Tester. In this case, you’ll get the exact figures. However, this method implies that you have to test your car battery when it’s under the load. Why is it the best method?

The voltage rate can have 3 parameter: rated battery voltage, working battery voltage and on-load battery voltage.

The rated battery voltage is the figure you can see in the specifications of your car battery or various books. It’s amounted to 12 V. Actually, there is a big difference between this figure and the figure of the working battery voltage.

The working battery voltage is the figure we’ve already mentioned in this article. You already know that the standard working battery voltage of a motor-vehicle meant for the transportation of passengers amounts to 12,6 – 12,8 V. Actually, the figure corresponding to the working battery voltage of your car battery may range from 12,4 to approximately 12,8 V.

As for the figure corresponding to the on-load battery voltage, it is very different from the figures mentioned above.

The method of testing is very simple. You need to use a special tool called Battery Load Tester. It creates a load on your car battery that’s twice higher than its capacity. The idea is to imitate the load that occurs when you’re starting the engine of your car. The figure you get as a result will show you not only the level of your car battery charge, but also its working capacity. It’s very important because a car battery shouldn’t only be charged, but it also should keep its charge under the load that occurs when you’re starting the engine and when the engine is turned off.

The most important tool you need to have in order to test your car battery according to this method is a Battery Load Tester.

battery load tester

You can buy this measurement instrument in any car store. A Battery Load Tester consists of a ballast resistor of high capacity, a voltmeter, 2 thin gages and a pin connector.

A Battery Load Tester allows you to test a car battery under load or without it. In the last case, you’ll use it as a voltmeter.

Before you start the procedure of testing, you need to disconnect your car battery from the charger and leave it as it is for several hours. Actually, you’d better leave it as it is for the nighttime.

Now, you can test your car battery when there is no load. You need to connect the positive thin gage of your Battery Load Tester (a wire with a terminal) to the positive car battery terminal. After it, you need to touch the negative car battery terminal with the metal pin connector of the Tester. The metal pin connector is negative. On the display of the voltmeter, you will see a certain figure. Using the table provided in this article, you can find out to what percent of the car battery charge level it refers.

test a car battery

If your car battery is 100% charged, you can start load testing it.

Attention! In order to get the valid data concerning the state of your car battery, you need to test it only when it’s completely charged.

 

If you use this method too often to test your car battery, it may result in its state becoming worse because there occurs load on it!

5. How to Test a Car Battery with Battery Load Testing

This method is used only when a car battery is 100% charged (a voltmeter should show the figures ranging from 12, to 12,9 V).

– You need to check that the terminals are disconnected from the car battery; – The positive thin gage of a Battery Load Tester (the red wire. Some models of the Testers are designed so that it’s the only wire they have.) should be connected to the positive output of your car battery; – After it, the negative thin gage should be connected to the negative output of your car battery. Pay attention to the fact that some Battery Load Testers don’t have the negative output (the black terminal). Instead of it, there is a pin connector on the other side of the tool. If you have a pin connector on your Battery Load Tester, you need to touch the negative car battery output with it.

test car battery load tester

Pay attention to the following key point in this method – the tool should be working for no more than 5 seconds after it is connected to the car battery. You need to take into account the figures you’ll see on the 5th second of its functioning.

When touching the negative output of your car battery with the pin connector, there will be sparks. It’s fine. Everything is right the way it should be.

If your car battery is in good condition, the voltage rate will fall down up to 10 – 10,5 V. After the voltage rate fall down and you disconnect the tool, the voltage rate should increase a bit. If the voltage rate falls down up to 9 V or more, you probably should start thinking of replacing your car battery with a new battery.

Below you’ll find a table showing the level of your car battery charge according to the results you get after the car battery load testing procedure.

level of car battery charge after load testing

Write us a feedback and say what method of testing a car battery you like the most.

The Video about How to Test a Car Battery Using Battery Load Tester

The Video: How to Test a Car Battery with a Multimeter

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