Can A Car Battery Read Good But Be Bad?

Key Points:

  • It is often times possible for a battery to show perfect readings but actually be of bad battery health.
  • This is often the case for faulty charging indicators.
  • To check for proper readings a multimeter has to be used following certain key steps.

There is a common question which every car owner has thought to himself at least ones, can a car battery read good but be bad?

Yes, it is completely possible for a battery to test well but actually turn out to be bad. The battery must attain a maximum voltage of 10 volts in this situation. The cell will die if the battery is charged at 5 volts.

In this article I will discuss why often times battery chargers show that a battery is fully charged yet it does not start the vehicle, as well as how to test battery voltage and battery health etc. So sit tight.

Is It Possible for A Battery to Read 12V and Still Be Bad?

A battery could be showing a voltage higher than 12 volts and still be bad. If it is bad, it will die or drop significantly when put under load.

If the battery measures 12V with no load it is bad or badly in need of a charge. If it reads 10.5V or less when under starter load, you need a new battery.

So, can a car battery read good but be bad? Yes, without a load, a faulty battery may easily yield 12+volts. It is rather the voltage under a load that matters.

When you try to start the automobile with a dead battery, the lights will become extremely dim.

As long as battery voltage remains above 9.6 volts, the battery is considered “good”. But if it drops below 9.6 volts by the end of the test, the battery may be “bad,” or the battery may have to be recharged and retested if it was not fully charged prior to the test.

Resting fully charged 12-volt batteries are around 12.8-12.9 volts, and flat dead ones are at 12.0 volts, so 12.4 volts on a resting battery means it’s about 50% charged.

A fully charged battery will normally register between 12.6 and 12.8 volts on a voltmeter. If the voltage on your voltmeter is between 12.4 and 12.8, your battery is in good health. Any voltage more than 12.9 volts is a sign that your battery has excessive voltage.

How to Use a Multimeter to Check a Car Battery?

When your automobile won’t start, it’s usually due to a low or dead battery. Most car owners, however, do not inspect their batteries until it fails.

Conducting a car battery voltage test using a multimeter on a regular basis – at least twice a year – is recommended as preventative maintenance.

Step 1: Preparing the battery

The first step is to find the car battery (see the owner’s handbook) and inspect the positive and negative terminals for dirt or corrosion.

The positive terminal is commonly identified by a red cover with a “plus” symbol, whereas the negative terminal is identified by a black cover with a “minus” sign.

Corrosive buildup should be scraped away with fine-grit sandpaper to prevent the multimeter from taking correct voltage measurements.

To protect the skin from dangerous chemicals and battery acid, gloves should be used. After the terminals have been cleaned, they will be used to connect the probes of the multimeter.

Step 2: Setting Up the Multimeter

The multimeter’s different measurement settings make it appear sophisticated, yet the overall operation is straightforward. The multimeter dial should be set to “20 volts” for evaluating the electrical output from a car battery.

However, before using the multimeter, all surface charge from the battery must be removed in order to get an accurate result. To do this, turn on the headlights for roughly two minutes before turning them off.

Step 3: Measuring and Analyzing

The multimeter includes two probes for monitoring battery load: red and black. The positive terminal is probed with the red probe, while the negative terminal is probed with the black probe.

The multimeter display should show a reading of 12.2 to 12.6 volts when the probes touch the terminals when the automobile is turned off and the battery is resting (full charge).

This voltage range indicates 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, indicating that it should be charged or replaced.

It’s time to get a reading on the crank cycle once the resting voltage has been determined. Because of the increased quantity of energy required to run the starting motor, this is the time when the car is turned on 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 voltage measurement will dip for a brief while when the automobile is turned on, but it should not go below 10 volts.

If the voltage drops below 10 volts, the battery has insufficient turnover strength and is likely to fail. The battery may need to be recharged or replaced in this instance as well.

The car will begin to idle immediately after the crank cycle and sustain a constant draw from the battery. When the motor is operating, the multimeter reading should be between 14 and 14.5 volts.

When the battery voltage drops below 14, it signifies the alternator is malfunctioning or the battery is weak and unstable for long-term vehicle operation.

While the car is running, the alternator’s purpose is to create energy to feed the electrical system and charge the battery.

Step 4: Testing the Alternator

Turn on all of the vehicle’s electrical equipment, including the headlights, interior illumination, climate controls, and audio, to test the alternator. The voltage load will be maximized as a result of this.

If the multimeter reading falls below 13.5 volts, the alternator is not charging the battery adequately and may need to be replaced. It’s time to get a second opinion from a certified professional.

A multimeter can offer crucial information about a vehicle’s battery and electrical system to its owner. Periodic testing can aid in the prediction and prevention of impending failures, which frequently occur without notice.

What Does the Battery Light Indicate?

It’s time to dispel a prevalent misunderstanding. The battery light on your device does not signal that there is an issue with the battery. When you start your automobile, it’s common for the battery light to come on and then go out.

However, if it turns on while you’re driving, it’s a clear sign that something is wrong with your charging system, which is usually the consequence of a malfunctioning alternator.

The duty of your battery is to start the automobile; your alternator is responsible for generating the electricity that keeps it running and recharges the battery.

A more useful interpretation of the battery light is that it is telling you that your automobile is solely running on battery power.

You will be able to continue driving for a short time if this occurs. You’ll notice that your electronic systems begin to shut down if you do. Your headlights will most likely fade, and you may lose seat warmers, radio, and other amenities.

This is because you won’t be able to drive for very long on battery power alone, you should limit your driving time.


So, now that you’ve read through the entire article, your question, “can a car battery read good but be good”, must have been answered. It also went through the steps of checking the battery voltage with a multimeter.

The first condition for a smooth functioning of an automobile is a good battery. Knowing that a battery can test fine yet turn out to be defective will enable you to charge or replace it before it is too late.

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