How to Test a Car Battery with a Multimeter – Detailed Step by Step Guide (Upd. 2020)

Isn’t it frustrating when your car battery betrays you and you end up stranded somewhere? This can be because of the dead or corroded battery. So, you should check the status of the battery beforehand, better be proactive rather than reactive.

However, if you are wondering how you can test the car battery, then all you need is a multimeter and this guide will walk you through it.

how to test a car battery with a multimeter

What Does a Car Battery Test Usually Include?

As a vehicle owner you should know how to test a car battery, but if you don’t then no need to worry, because in this easy to follow guide we have gathered some major tests that you can conduct on your car battery in order to check its status. So, some important tests include:

  • Testing a car battery with a multimeter.
  • Testing car battery’s terminals with a multimeter.
  • Conducting battery leak test with a multimeter.
  • Testing alternator with a multimeter.
  • Testing the cold cranking amps (CCA) of a battery with a multimeter.

All the above mentioned tests will help you figure out what is going on with your car’s battery and also help you to resolve the hard-to-start or no-start engine issues.

How to test your car battery with a multimeter? 

It’s a great idea to keep a regular check on your car battery’s performance in order to avoid any inconvenience. So, for this purpose you might need a digital multimeter and it will take less than a minute to check the status of the battery.

What you need is a digital multimeter and then follow these simple steps:

  1. First, turn the ignition off and remove the battery’s positive cover.

2. Set your multimeter to DC setting and if it does not auto-range, then select 20 DC volts.

3. Now, it’s time to test the battery – connect the positive red probe with the positive terminal of the battery and the black probe with the negative terminal of the battery.

4. A healthy battery should have a charge about 12.6 volts, if the battery’s charge is way less than this benchmark then the battery needs to be recharged or replaced.

5. Now, turn on the headlights and check the reading again. You’ll see a drop in the voltage reading which can be about 12.5 volts. But, if it is 12.3 then it suggests that battery is 75% charged, and if it is not anymore than 11.8 then your car battery holds only 25% charge.

how to test a car battery with a multimeter

How you can check your car battery terminals by using a multimeter? 

You certainly have experienced some issues while starting the engine. So, have you ever considered that the problem can also be with the car battery terminals? As, corroded, dirty or loose battery terminals may lead to some engine issues and these are sometimes hard to find via visual inspection.

So, a multimeter can also help you in this arena too and will allow you to check the faulty battery terminals. All you need to do is follow these simple steps:

  1. First, you need to disable your car’s ignition system, which can be done by disconnecting the ignition coil or by removing the rely or the fuse for the fuel pump.
  2. Place the tip of red metal probe of your multimeter on the positive battery terminal post and the black metal probe to the other terminal connecting the same battery post.
  3. Now, ask someone to start the engine and check the voltage reading on your analog or digital multimeter. If it reads more than 0.5 volts, then there’s a chance that your car positive battery terminal post is dirty or corroded.
  4. Repeat the same process for the negative battery terminal post, but this time touch the terminal post with the black metal probe first and then with the red one. And ask your assistant to crank the engine again. Now, check your multimeter – if it reads over 0.5 volts, that indicates that there’s something wrong with the terminals and you need to clean them. 

With the help of a multimeter, how can you do a leak test on the battery cover? 

A battery leak can discharge your battery quickly and can get you in trouble. Actually, it’s the dirt and acid mix that accumulate across the terminals and causes the battery charge to leak slowly.

Another abnormal electrical loss on your battery includes ‘parasitic loss’ – some electrical components of your car use the current even when the engine is turned off.

However, you can use a multimeter in order to check whether or not the car battery has reached the leaking phase. So, what are you waiting for? Grab your multimeter and follow these steps:

  1. First, turn on your multimeter and set it on the voltage setting.
  2. Now, touch the multimeter’s black probe with the negative terminal of the battery and the red one with the dirty corroded battery cover.
  3. If your multimeter reads even a small amount of voltage, then you need to clean the car battery as the buildup is drawing the battery power.

Whereas, if your multimeter reads zero voltage, but you still suspect that your battery charge is draining quickly then check for parasitic draw.

How can you check the alternator by using a multimeter? 

Alternator is an essential unit of any vehicle’s electrical system, and it charges the battery when the engine is running. As the name suggests, alternator also provides power to different electrical components of your car and, in turn, reduces the load off the battery. 

However, your multimeter can check the status of your car’s alternator too. Testing the alternator is pretty much the same as testing the car’s battery. All you need to do is follow the following steps:

  1. Connect the probes of your multimeter with the alternator, but this time check it with the engine running at its idle speed.
  2. Now, check the readings on your multimeter. If it reads between 13.8 volts and 14.4 volts then there’s nothing to worry about. 
  3. But, if it is less than 13.8 volts then the battery is undercharging, while if it is above 14.4 volts, it is overcharging.

In either of the above situations – undercharging and overcharging – the lifespan of your car’s battery is decreasing and requires necessary actions.

How you can test the cold cranking amps (CCA) of a car battery with the help of a multimeter?

Cold cranking amps (CCA) is used to trigger the ignition and will tell you if your car can successfully draw power.

So, if you are looking towards measuring CCA of your car with a multimeter, then follow these steps:

  1. First of all, connect your multimeter with the battery via probes and then ask your assistant to crank the engine. 
  2. Now, check the readings – in an ideal case, the value should first drop around 10 volts and then return to a higher value around 12 volts or more.
  3. Whereas, if the reading remains constant while the engine is still running, that indicates that your battery is as neat as a new pin.

However, if the initial reading of CCA on your multimeter is around 5 volts, it suggests that your car’s battery will not last longer and if it reads way less than 5 volts, then it is time to replace the old battery.

Final Thoughts

As you have already seen how easy, simple and quick it is to test your car battery with a multimeter, so now you can do it yourself and save your time and money. Not only this, you can help your fellows in diagnosing their battery problems and be a domestic hero.

Hope you have found this article useful, if you have any questions let us know in the comments.

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