How to Test a Car Battery with a Multimeter

You’re running late and about to leave, and when you jump in the car to start it, your engine just doesn’t want to start. You think that the problem might be the vehicle battery, but are you sure?

The car battery is one of the most important parts of your vehicle. Regularly testing your battery is essential, not just when it starts to show issues.

If you don’t test it, it will most probably leave you stranded. Most manufacturers recommend battery testing at least twice a year, whether done by a professional or by yourself.

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That is why knowing how to test a car battery with a multimeter is very beneficial. You save the cost, as well as time with making an appointment of having it checked by a mechanic.

To be able to avoid all the hassle of battery failure, the cost and your time, here are the things you need to know how to test a car battery with a multimeter yourself:

What is a Multimeter?

A multimeter, otherwise known as Volt-Ohm Meter, is a handy device mostly used by electricians to measure electricity. It can measure voltage, current, and resistance. There are two types of multimeters: an analog and a digital multimeter.

Digital is more widely used since they are more convenient since the output is displayed on the LCD screen. Below is a picture of a digital multimeter, but there are many different multimeter models available in the market.

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There are three main essential parts of a multimeter:

  1. Display. The LCD screen is where the output is shown. It usually has an ability to display a four-digit result and a negative sign, if the output is negative.
  2. Selection Knob. This is a feature where the user can set the device to read different things, such as current, voltage and resistance.
  3. Ports. It is found in front of the unit where the two probes, COM, and mAVΩ, are plugged in.

What You Will Need?

The following are a few tools you will need to successfully and safely test your car battery:

  • Digital multimeter or Analog Multimeter. You can use whichever is available, but digital multimeters are more commonly used nowadays due to their convenience.
  • Safety glasses. For security purposes of the eyes.
  • Electrical Safety Gloves. This is a necessary safety wear when performing electrical works.

Learn How to Test a Car Battery With a Multimeter

Checking your car battery voltage is fast and easy using a multimeter. You just need to follow a few steps to perform it successfully.

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  • Turn It Off. Make sure the ignition and the lights are off.
  • Set the Multimeter. Set it to 20 DC Volts.
  • Uncover Terminal. Remove the cover of the positive terminal of the battery.
  • Negative to Negative. Attach the multimeter’s negative/black probe to the battery’s negative/black terminal.
  • Positive to Positive. Connect the multimeter’s positive/red probe to the battery’s positive terminal.
  • Load a Light. Ask someone to turn on the headlights to put a load in the battery.
  • Check the Output. Check the multimeter reading.

What Does the Multimeter Output Mean?

Now that you know how to test a car battery with a multimeter understanding the results of the multimeter is necessary. To fully determine the condition of your battery, note the reading on the multimeter and refer to its equivalent below:

  • An output of about 12.5 or higher, indicates that your battery has a good state of charge.
  • An output of about 12.3, indicates that your battery is about 75% charged and is still in a relatively good condition.
  • An output of about 11.8 or lower, means that your battery is about 25% charged or less. Which means that it needs to be recharged, or worse, needs to be replaced.

These readings are meant for a car battery at 80 Fahrenheit. The voltage will change at .01 volts for every 10-degree temperature change.

When Do I Need to Change My Car Battery?

Followed all the steps on how to test a car battery with a multimeter, and got a low output? How do you know when you already need a battery replacement?

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While getting a new car battery seems to be the best option, you do not want to jump to the conclusion that a low output indicates a need to replace your car battery right away.

There is one way to figure it out. If you got a low output, charge your battery slowly. This is for the battery’s chemical reaction to improve. After charging, repeat the steps on how to test a car battery with a multimeter, if you still got the same output, or lower, that’s the greatest indicator that your vehicle needs a new battery.

Follow the steps on how to change a car battery.

Once you already know how to test a car battery with a multimeter, you will be able to check your vehicle battery and monitor its state regularly. So, no need to worry about getting stranded, and being late due to hard starting.