How to test the car battery by yourself?


Your dashboard and lights are turned on, but the car cannot start? When you try to start the car, do you hear a clicking sound or the dash indicator dimming? If you notice any of these symptoms, it may be that the battery is bad. Before replacing an expensive car battery, it is best to check the battery to make sure it is really bad. Otherwise, you may replace a high-quality battery for no reason.

In this article, as a car battery supplier, we introduced how to use two methods to a car battery:

1. Digital Multimeter

2. Battery Analyzer

How to test a car battery with a multimeter?

Testing car batteries is simple and requires a digital multimeter. If you have never used a multimeter, please don’t worry because it is very simple.

In short, you need to set the multimeter to a 20 volt DC current setting. Then, turn off the ignition and lights. Connect the red cable to the positive (+) terminal of the battery and the black cable to the negative (-) terminal of the battery.

Turn off the ignition

To test the car battery with a multimeter, you need to turn off the engine.

Locate car battery

The first step in checking a car battery is to locate the battery. In most cases, the car battery is located in the engine bay. Open and look for the battery near the engine.

If you have a European car or a high-end luxury car, the battery is most likely in the trunk. Some models of batteries may be located under the passenger seat or under the rear cushion.

Can’t locate the car battery?

If the car battery is hidden under the seat or installed in a hard-to-reach area, you can use the jump-starting terminals to connect a multimeter. You may notice that the voltage difference between the battery and the jumping posts is 0.0 to 0.2.

Set the multimeter to the 20 volt setting

Set up a multimeter to measure voltage. Most multimeters have two voltage settings. One is direct current (DC), with a straight line at the top of the V symbol. The other is alternating current (AC) with ~ above V. The ~ symbol represents a sine wave.

The car battery generates direct current, so make sure to set the voltage of the voltmeter to V and use a dash (-) at the top. Plug the cables into the two ports of the voltmeter. These are called test leads in technical terms.

Connect the positive probe

The red cable or wire of the multimeter should be inserted into the + port and connected to the positive terminal of the car battery.

Connect negative

The black cable should be connected to the terminal (negative, ground) of the digital multimeter and the negative of the car battery.

Measuring voltage

After turning on the multimeter and setting the voltage range properly, the multimeter will show the battery voltage.

Determine battery status

Determine if the battery is charged or not.

Battery voltage guidelines

Voltage Status
Engine Running: 13.7 to 14.7 volt GOOD
Engine Off Charge Status
12.6 or more volts 100% Charged – GOOD
12.4+ Volt 75% Charged – GOOD
12.2 – 12.4 Volt 50% Charged – Needs Charge
12.05 Volt 25% Charged – Needs Charge
Under 12 volt Battery Discharged

Just because the battery reads more than 12.6 volts, it does not always mean that the battery is good. The battery may read more than 12.4 volts, but the output cold start current (CCA) is not enough to start the car. In the next section, you will learn how to perform a battery load test.

How to load test car battery?

Any auto repair shop or even some auto parts shops can carry out battery load tests for you.

It cannot be assumed that the battery itself is damaged because the battery has been discharged. This is inaccurate. To determine if the battery is good, charge the battery and perform a load test.

During the load test, the car battery needs to provide at least 9.5 volts during engine start. The battery needs to be fully charged to perform the load test accurately.

Checking the voltage may cause misleading, because the battery may test well according to the voltage, but cannot hold the load.

In modern vehicles, load testing is a better way to determine whether the battery is good or needs to be replaced.

Use a multimeter to load test the car battery

1. Connect the multimeter probe to the car battery.

2. Set the voltmeter reading to automatic detection or 20 volts.

3. Note the battery voltage with the engine off.

4. Start the car and pay attention to the voltage drop on the multimeter. (It’s fine if the car doesn’t start.)

5. If the voltage drops from 12.5 volts to 10.5 volts during starting, for example, less than 2 volts, the battery is good.

6. If the voltage drops more than 2 volts or less than 9.5 volts during the starting process, the battery needs to be replaced as soon as possible.

The best way to test car batteries

The easiest way to test a car battery is to use a battery analyzer, also known as an electronic or conductivity tester.

The electronic tester sends an AC frequency signal through the battery to determine the condition of the battery. In old batteries, the current and conductivity of the inner plate of the battery may be low.

In other words, the electronic tester measures the conductance of the battery cell.

Some but not all battery analyzers can measure the cold start current (CCA) of the battery.

By measuring the CCA capacity of the battery, the remaining life of the battery can be determined.

The best way to charge a dead car battery

Many car owners simply start the car and let the alternator charge the battery.

In most cases, although the alternator is used to charge the battery, this is not the best way to charge the car battery and will shorten its life.

The alternator in a car is designed to provide voltage to drive the car and not to charge a dead battery. There are two reasons why you should not use an alternator to charge a car battery.

Reason 1

If the battery is completely exhausted and you want to jump start the car, it may cause an electrical fault, trigger the under voltage fault code on the vehicle control module, or even make the car enter the limp mode.

Reason 2

Fast charging, such as the alternator charging the battery, is unhealthy for the battery. If you want to charge the battery to 100% properly, use the slow charging method.

A trickle charger takes longer, but will make the battery enter a fully charged state.

To properly charge the car battery, you do not need to remove it from the car. Even removing or disconnecting is the preferred method.

1. Get any 12 volt Trickle charger.

2. Connect the red positive clamp to the positive terminal of the battery.

3. Connect the negative clamp to the negative battery terminal.

Note: Many vehicles have battery jump start terminals under the hood. In most cases, the car manufacturer recommends that you use jumper terminals to charge the battery.

If the battery is fully charged, the battery showing low voltage may still be a good battery. You need to check whether the battery can be charged to determine if it is good or bad.

To determine whether the battery is defective, follow the steps in the next section to perform a battery load test.

Symptoms of a bad battery

If your car battery does not charge or discharge when parked, the battery itself may be the culprit.

In most cases, the battery is obviously broken, but sometimes the battery problem is not so obvious

• Battery indicator lights

• The car won’t start

• Click, click, click when trying to start the car.

• The engine rotates slowly

• The battery cannot be charged

So now, all my dear friends know how to test your car batteries now?

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