The fact a car battery has an average working lifespan of between three to five years gives car owners a lot of confidence when driving. This is the reason why you are likely to be rendered speechless the moment your battery fails to start your car. Despite several attempts to start the vehicle, all you hear is a click. Your battery may be failing but for you to be sure you need to know how to test a car battery.
I have always advocated for a reliable Multimeter to be one equipment that should always be in the toolbox. A Multimeter is a device that you can use to check the state of your battery regarding voltage and current.
To put your immediate fear to rest this device can test the battery load and current charge capacity. As you use this article to troubleshoot your battery let’s hope that at the end of the step by step tutorial all you will have to do is to charge and not to make plans to purchase a new battery.
Your battery may also fail due to poor maintenance and a combination of weather elements such as cold.
What You Will Need
Testing a car battery requires very simple routine steps and as such the tools and equipment needed are also very basic. Always take care when testing the car battery, make sure you turn off the car completely including its accessories.
- Gloves for hand protection against corrosive acid or potential spillage
- Goggles to protect your eyes
- A digital Multimeter
- A voltmeter
How to Test a Car Battery? Step by Step
Step #1: Open the Hood To Expose the Battery
The most likely place to find your car battery is in the front trunk. Some cars have batteries installed in different locations such as under the driver's seat or one of the back seats.
Step #2: Set up the Multimeter
Set the voltmeter to read up 20 volts. Car batteries range between 12V and 24V depending on the car model. But in this case for a small car, you set upper range value to anything higher than 12V. Let the negative terminal of the Multimeter touch the negative terminal of the battery as the positive one touches the positive terminal.
NOTE: The positive and the negative terminals of the Multimeter are indicated by the red and black colors on the probes.
Step #3: Get the Readings
All battery readings have a range of values that you can use to determine the state of the battery. At room temperature (about 25C) you should expect readings in the following ranges
- Any reading above 12.5 Volts means a fully charged battery and your car should be able to start the vehicle.
- Any reading that is between 11.9 to 12 Volts means that your battery has at least 75% of charge left.
- If you have a reading below 11.9 Volts, you have to charge your battery and do the testing one more time.
One thing you need to note from these readings is that they only show the battery’s current state of charge and not its performance or load capacity.
Step #4: Recharge the Battery
If you get lower voltage readings which indicate low charge capacity, you can take the battery to the nearest auto shop for recharging. If you have a portable battery charger, well and good.
Step #5: Comprehensive Testing
The initial test was able to give you the current charge capacity. This second phase of charging is meant to give you an indication of whether the battery is good or due for replacement. To do this test, first of all, you will do a battery load test.
Step #6: Testing the Battery Load
This step can be done using a load tester which will simulate load on the battery while the tester gives voltage readings. During this test, if you get a voltage of 9.5 and below, the battery needs to be replaced.
The second load testing option is through the use of an electronic tester which sends frequencies through the battery and through these readings you can tell the condition of battery cells.
NOTE: If you do not have access to either a load tester or an electronic tester, you can have another person turn on the car headlights to full glare and as you read the Multimeter.
Testing a car battery for both charge and load capacity was that simple and straightforward. There are other simple tests that you can also do to check the overall state of the battery.
Battery Maintenance Tips
The following are a list of things that I would consider to be very essential to improving battery performance.
Battery Terminal Test
Your battery may exhibit characteristics of a dead battery not because it is dead but because its terminals are dirty or corroded. Regularly check the battery terminals for loose connections and rust. This is the primary reason why your car may fail to start.
To check the terminals if they can cause a voltage drop do the following:
1. Disable the Ignition
Disconnect the ignition coil (kindly consult your owner’s manual for the exact location of the ignition coil) this is to make sure that the car does not start when you start the engine.
2. Connect the Multimeter
Attach the positive and the negative terminals of the Multimeter to the battery and ask another person to start the engine and register the readings. A reading of 0.5 and above is an indication that you need to clean the terminals.
Battery Leak Tests
Battery leak test in simple terms means checking how much dirt has accumulated on the battery cover. Too much dust or rust causes charge leak, and this may cause problems when starting the car. To do this test using a Multimeter, you will:
- Set the Multimeter to the lowest reading on the volt scale
- Turn on the Multimeter as you probe the battery negative terminal using the black (negative) terminal and as the red (positive) terminal probes the battery cover. If your Multimeter can detect even a small amount of voltage, that’s an indication that your car battery is leaking.
To sort out a charge leak is the simplest thing you will ever do in battery maintenance. Just wipe the dust off and scrape off the rust build up.
Investigate the Battery Case
A broken, damaged or leaking battery case is a potential danger in waiting. From the possibility of corroding the engine components and permanently rendering battery useless, checking the status of the battery is a vital part of battery maintenance. To do a case cover test, you need to remove the battery from its assembly and perform the following tests.
- Unscrew the battery assembly and remove it from the tray
- Place the battery on a wooden bench or any flat wooden surface
- Look for any visible signs of leakages and cracks. You should also examine the terminals for damage. Any swellings should also be noted
- Check the entire battery assembly for worn out cables and the state of the battery assembly
The article has covered a comprehensive battery test and analysis. The work can be easier if you have the right equipment. To avoid disappointments, you need to check the state of your battery regularly. I hope the article has been able to cover all aspects of the car battery testing and maintenance. In case you have additional points that I may have left out do not hesitate to share it with us. If the article has been helpful to you, please share it.