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How to Test Car Battery Amps With Multimeter? – 3 Steps

Written by Edwin Jones / Fact checked by Andrew Wright

how to test car battery amps with multimeter

Car batteries are in charge of powering all of a car’s electrical components. When it is full, you should have no problems utilizing it. However, issues with the battery can disrupt all critical electrical functions, including the engine’s cranking.

In this article, I will provide a thorough guide on how to test car battery amps with multimeter, so you’ll know if it’s still working.

Step-by-step to Test Car Battery Amps With Multimeter

checking-a-battery-with-a-multimeter

What To Prepare

  • Chemical-resistant gloves
  • Eyeglasses or any protection for the eye
  • Multimeter

Additional tools for other methods of measuring amps.

  • Clamp meter
  • Battery tester
  • Voltage meter

Step 1. Setup the Multimeter

To test battery with multimeter and get its amp rating, you need to set up your multimeter first. Set the dial of the device at an amp setting.

Next, you need to connect its black lead to the common terminal and, at the same time, connect the red lead to the amp terminal of the multimeter, since we are working with more than 10 amps of loads.

After adequately preparing this setup, you can now check battery amperage output.

Step 2. Performing the Test

When you use multimeter to test battery CCA (Cold Cranking Amps) rating, it is better to have someone start the engine. This is necessary, since you need to see the actual amp reading of the current produced by the battery during startup.

Once the engine is on, connect the red and black leads of the multimeter to the positive and negative terminals, respectively.

Step 3. Comparing the Result

After you measure battery capacity, you can compare it to your battery’s CCA rating. If the rating is lower than it should be, you might need to replace your power unit as soon as possible.

This CCA rating refers to the cranking amps capacity of a battery under cold temperatures. If it is low, there is a high possibility that your car won’t start, especially during winter when your vehicle needs more power to start its engine.

Other Ways to Get the Battery Amp Rating

1. Using Clamp Meter

A clamp meter is an easy way to test the amperage of your car battery. This device performs the same function as a standard digital multimeter. Just clamp this device over the positive wire and check the reading on its monitor.

2. Using Battery Tester

A battery tester is another useful tool for determining the battery amps. One advantage of this device over a multimeter is that it can provide more information. It can give the actual charging state, voltage, and CCA rating.

To use this tool, hook its clamps onto the battery terminals, then enter information about your battery, so the device can start testing.

2. Voltmeter Battery Test

Checking the battery with voltmeter is a good idea to know its state of charge. Furthermore, it can also help to determine whether your battery needs a replacement.

To test battery capacity, you only need to connect each wire of the voltmeter to each terminal of the battery, and you can read the actual electrical reading on its monitor.

  • Tips: If you think your battery is bad and you have a maintenance-free battery, there is nothing you can do with it.

However, if your battery can be serviced, you can check the battery cells to see if there is enough water inside. If the moisture level is low, you can add distilled water.

How to Test a Car Battery Without a Multimeter?

test-battery-with-multimeter

Without multimeter, it is hard to determine the battery condition precisely. However, if you only want to know if your battery is working normally, you can follow the steps below.

1. Check the Battery Visually

Visually inspect your battery to determine if there is any corrosion on the terminals or leaks anywhere. If everything appears to be in order, you can move on to the next steps.

2. Test the Battery

To test your battery, turn on the headlights, but do not start the engine for at least 15 minutes. If the battery is in good condition, there should be no issues such as dimming lights within this time frame.

Symptoms of a Poor Battery

An old car battery often needs to be replaced. However, aside from that, several signs will appear before it is entirely dead. Some of the symptoms of a failing battery include:

1. Slow to Start

A bad battery is usually to blame for the delayed start of a car engine. If it takes forever for your vehicle to get moving, a multimeter battery test is in order. If jump-starting your car doesn’t work, a trip to the mechanic is probably necessary.

2. Won’t Start the Engine

Another sign of a faulty battery is the inability to start the engine. Instead of being slow in its operation, the battery doesn’t seem to work at all.

3. Some Lights Work But the Engine Don’t

You may also notice that the power of a battery is insufficient to crank the engine but sufficient to power various accessories. In this instance, you should test car battery CCA or use a jumpstart method to start the engine.

4. Frequent Need For Jumpstarts

Obviously, if you frequently jumpstart your car, you may have a serious battery problem. It is possible that your battery is unable to keep a charge. However, you should also check to see if any devices like radios are draining your battery charge.

5. Heavy Corrosion in Terminal

Finally, inspect both terminals of your battery for corrosion or leaks. Both conditions may reduce its efficiency in supplying the loads required by your vehicle.

In this case, cleaning each terminal and checking a battery with a multimeter on a regular basis is the wisest thing you can do.

Helpful Tips/FAQs

1. What Should a 12V Battery Read When Fully Charged?

If you test a 12v battery and see a reading of 12.6 or above, it means your battery is fully charged. However, if the battery voltage is 12v or below, your battery has no power left.

2. What is the Voltage at Which a Car Battery Needs to Be Replaced?

If you want to check car battery health, getting a voltage reading is the best way to do it. Normally, a car battery that is in good condition should read 12.4v to 12.9V. If you got a reading of 9.5v, you might need to replace the unit.

Moreover, some experts say that it is best to replace a car battery once it gets three to four years old.

3. How Long Should You Run a Car to Charge the Battery?

Typically, the alternator needs at least 30 minutes to recharge a battery after starting. However, recharge may take longer if your car battery is empty or flat and you can only drive at 1000 RPM or lower.

RPMs and their corresponding speeds can differ from car to car, so it’s hard to give an estimate. For instance, 1000 RPM may equal 16.5 mph for one car but 40 mph for another.

 4. How Many Amps Should a Car Battery Have?

The normal amps for car battery often range from 400 to 1000 CCA, and the bigger the vehicle, the higher the amperage tends to be. For accuracy, it’s best to check your car manual.

Conclusion

Knowing how to test car battery amps with multimeter will give you an idea of how much load it can draw. Moreover, it will also help determine the health of your vehicle’s power source.

In addition to cars, you can use this device to check AA battery amps as well. Just switch the dial setting to mAh (milliamp hours), since you’re working with a smaller battery size.

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