How to Test Car Battery with Multimeter

When your vehicle doesn’t start, it’s usually due to a low or dead battery. Sadly, most vehicle owners do not inspect their batteries until they fail. Nevertheless, it is a good idea to battery test your car frequently to ensure that it is still functioning well. 

A car battery test ensures that your car is ready for a long, and even a short drive. And using a battery multimeter is an excellent way to do so. It will offer you a decent indication of whether or not you will need to replace it soon.

In general, car battery testing with a multimeter can be done in simple steps:

  • Turn off your car and remove your test battery. 
  • Attach the positive probe to the area with a red cover with a “plus” sign, and put the negative probe to the area with the black cap and “minus” sign. 
  • Use the multimeter to read and measure the battery voltage.

The Multimeter should display 12.2 to 12.6 readings to verify that your car battery is still functioning well. Whereas, If the recorded voltage is less than 12.2 volts, the battery’s resting voltage is low, suggesting that it should be recharged or replaced.

Thankfully, this is a straightforward task. There’s no reason you can’t perform it all alone if you have the necessary equipment. Read along as I show you the following steps on how to test a car battery with a multimeter.

Step 1: Get the Test Battery Ready

car battery

The first step is to identify the vehicle battery and inspect the positive and negative terminals for contamination or deterioration. A red cover with a “plus” sign commonly identifies the positive terminal, whereas a black cover identifies the negative terminal with a “minus” sign. It is crucial to properly link them to their correct terminals for you to have an accurate test result.

The corrosive coating should be scraped away with fine-grit sandpaper to prevent the multimeter from taking the correct voltage readings. To cover your skin from harmful toxins and battery acid, you should use gloves. After you clean the terminals, you may use them to link the multimeter’s probes. (1)

Step 2: Configure the Multimeter

multimeter set

The multimeter’s different measurement configurations make it appear confusing, yet the overall operation is basic. The multimeter dial should be calibrated to “20 volts” to check the vehicle battery voltage energy.

However, before using the multimeter, you must first eliminate all surface energy from the battery in order to get an accurate result. To accomplish this, turn on the headlights for roughly two minutes before turning them off. (2)

Step 3: Measure and Examine

car battery test by mechanic with multimeter

There are two essential factors in measuring a car battery that you should consider. It is important that you should measure it while it is resting and in the crank cycle. 

This way, you can have more accurate results that can help you decide whether to change your car battery immediately or not:

Battery Testing while Resting

The multimeter display should indicate a reading of 12.2 to 12.6 volts when the probes contact the terminals while the automobile is off and the battery is sitting (full charge). This electricity range states that the battery is capable of starting the car. 

If the recorded voltage is less than 12.2 volts, the battery’s resting voltage is low, suggesting that it should be recharged or replaced.

Measure your Battery in the Crank Cycle

It’s necessary to get a measurement of the crank cycle too once you have calculated the resting voltage. Due to the increased energy required to run the starter motor, this is when the car is powered, and the battery is under the most strain.

A second person will be required to start the ignition in order to obtain this reading. The battery voltage will dip for a brief while when the automobile is on, but it should not decrease below 10 volts. If the voltage lowers to 10 volts, the battery has the insufficient turnover capability and is likely to fail. In this case, you may also need to reload or buy a replacement.

Bonus Step: Examine the Alternator

car alternator

The alternator’s purpose is to create energy to supply the entire circuit and charge the battery. So, switch on all of the vehicle’s electronic systems, including the headlights, interior illumination, weather controls, and stereo, to test the alternator. 

When done, it will maximize the voltage load. If the multimeter results drop below 13.5 volts, the alternator is not charging the battery adequately, so you may need to replace it. It’s time to seek a consult from a licensed professional.

FAQs

What are signs that my vehicle battery is failing?

The following are the most prevalent indications of a malfunctioning battery:

– The dashboard’s battery light is always running.
– When you first start the engine, it cranks gradually.
– The vehicle needs to be jump-started frequently.
– When you start the engine, it clicks.
– The lighting is faint.
– The car will not start.

What drives the battery to fail?

Heavy discharges, temperature, vibrations, rapid charging, and overcharging all increase the process of “aging” of a car battery. The reduction of water for normal recharge charges due to lack of maintenance, evaporation from excessive under-hood temperature, or overcharging contributes to almost half of all early automobile battery failures. 

Sudden failures are also caused by positive grid corrosion and undercharging, which causes oxidative stress. Positive grid corrosion causes an open connection in deep cycle batteries that are typically well handled and charged. Another reason is the erosion of active materials.

What is the average life of a car battery?

Vehicle batteries typically last between 2 and 5 years. The climate is among the most significant factors determining how long a car battery will last. A running engine underneath the hood is already generating a lot of heat. When you combine that with a blazing hot day, you will have a drastic drain on your car battery, which can contribute to a higher chance of a dead battery if you don’t take appropriate summer driving preventative measures.

Hot weather can cause liquids in car batteries to evaporate, causing the battery’s inner structure to deteriorate. As a result, ordinary battery life is relatively short in warmer climates. When evaluating how long your car battery will last, take into account the climate in which you will do the majority of your driving.

Properly caring for your car battery can help maintain the system despite the weather. Avoid short rides; your car’s battery will not fully charge if you use it frequently with short rides. Sustain the battery power in your automobile by driving it regularly and for long periods of time. 

Consider getting a portable auto battery charger if you don’t use your car very often. In the event that you become stuck, these portable chargers can kickstart your battery without the use of another vehicle.

What is the optimum voltage for a car battery?

The voltage of a good automobile battery should be around 12.6 volts. It’s crucial to test the battery after it’s been laying for at least an hour to determine what’s known as the ‘resting voltage.’ If you’ve been driving recently (and the charging mechanism is working properly), the battery will likely produce a more significant number than the resting voltage, which could be misleading.

Better yet, park the car overnight and examine the battery the following day to receive a more accurate picture of the charge state.

Other Common Car Battery Problems

car engine

A person’s car batteries might have a variety of issues. Here are a few examples:

  • A bad connection
  • Corrosion
  • Disuse
  • Problems with the alternator

Below are other battery and car learning guides that you might check. Until our next article!






References
(1) harmful toxins – https://www.health.ny.gov/environmental/
chemicals/toxic_substances.htm
(2) surface energy – https://www.sciencedirect.com/topics/physics-and-astronomy/surface-energy

About Sam Orlovsky

b1d87d2ee85af3e51479df87928bdc88?s=90&d=mm&r=gI realized early on carpentry was a huge passion for me and I’ve stayed in the industry for over 20 years now. This gives me a unique ability to really be able to tell you what the best tools and recommendations are. I’m not only a carpenter but I also like machinery and anything to do with electrics. One of my career paths starting off was as an apprentice electrician so I also have a lot of experience with electrical products and anything related.