How to Check for Battery Drain with a Multimeter (5-Step Guide)

People don’t often check their car battery for voltage drops but if done periodically it could be great prevention. This battery check is important to ensure that your car is working efficiently at any time.

This article will help you easily know how to check for battery drain with a multimeter. We will help you identify the cause of a battery issue and also how you can fix it.

Checking for a battery drain with a multimeter is simple. 1. Remove the negative car battery cable. 2. Check and draw across the negative cable and battery post. 3. Remove and replace fuses. 4. Isolate and fix the issue. 5. Replace the negative battery cable.

test car battery

Getting Started

You may purchase a new battery and discover that after some time, it is already dead or damaged. While this could be due to a couple of reasons, most of the time it is due to parasitic drain.

I am going to explain in detail what this is and why it is important to do a battery drain test to avoid any inconveniences and costs.

What is a Parasitic Drain?

using multimeter to test car battery

Essentially, this is when the car continues to draw power from the battery terminals even when the car’s engine is turned off. This could be due to many reasons. Since most cars today have many advanced auto parts and electrical equipment parts, a small parasitic drain is usually expected.

Parasitic battery drain reduces the lifespan of the battery. This is because it causes a voltage drop with time. This is why after some time, your battery dies for good, and the engine can’t start.

Luckily, battery drain is a problem that you can easily solve at home without incurring further costs. A parasitic battery will leave you frustrated since your car will not start and can leave you with other costs.

How Many Volts Should a Car Battery Have?

New and fully charged car batteries should have 12.6 volts. This is the standard voltage for all batteries. If your car does not easily start after turning the keys, then it means that your battery is weak and most likely needs to be replaced.

New car batteries can be bought from an auto parts store near you or an online trusted source. (1)

Below is a list of everything that you’ll need to do a battery drain test.

What You’ll Need

multimeter in yellow color

To do a simple drain test, you will need the following items at your disposal during the entire procedure.

  • A digital multimeter- This needs to measure at least 20Ampheres. You can get one at an online store or an auto parts store near you. I recommend going for branded multimeters as this guarantees the quality of the multimeter.
  • A wrench- This is to remove the battery terminals while checking for battery drain. The sizes can include 8 and 10 millimeters.
  • A pair of pliers- This is to remove the fuse from the fuse panel of the battery.

How to Check Car Battery Drain with a Multimeter

checking drain battery with multimeter

These are simple steps that you will need to follow correctly to avoid any mistakes that could prove costly to you.

To begin this process, you will need to first shut down your engine and remove the key from the ignition. Open the hood of your car. Turn off all electrical equipment that might be on. These include radio, heat/ air conditioning. The parasitic draw could be caused by some of these systems and that is why you need to turn them off first. Then follow these steps which include:

Step 1. Remove the Negative Battery Cable

You will need to remove the negative cable from the battery cable terminal. This is done to prevent shorting of the battery if you are doing the test from the positive end.

The negative cable is normally black. In some cases, you might have to use a wrench to unscrew the cable.

Step 2. Check the Draw Across the Negative Cable and Battery Post

After doing this, you connect the multimeter to the negative cable that you have just unscrewed.

To set the multimeter, you connect the black probe to the common labeled as (COM) input of the multimeter. The red probe goes into the amps (A) input hole.

To get the right results, I recommend you get a multimeter that can record a reading of up to 20 amps. This is because a fully charged battery will read 12.6 volts. Then set the dial to read amps.

After setting the multimeter, place the red probe through the metal part of the negative terminal of the battery. The black probe will go onto the battery terminal.

If the multimeter records a reading of about 50mA, this means that your car has a battery drain.

3. Remove and Replace Fuses

One of the most common methods for testing for parasitic battery drain is by removing all the fuses and replacing them one by one. This is done while still checking the readings of the multimeter.

Take note of any drop in the multimeter reading. The fuse that leads to a drop in the reading of the multimeter is the reason for the parasitic battery drain.

You will need to remove the fuse and replace it with another one if you are confident that it is the one causing the parasitic drain. If it is the only component causing the drain, you can remove it and then reconnect the battery.

4. Isolate and Fix the Issue

If you remove a fuse or a circuit and discover that it is the one causing the problem, you can narrow down the problem and fix it. If it is an entire circuit, you can remove the individual components while checking for the multimeter drop.

You might want to refer to the manufacturer’s blueprints so that you can know where each component belongs.

After isolating the issue, you can fix it yourself or if you are not sure, hire a mechanic to fix it for you. In most cases, you can just fix the problem by simply turning the component off or removing it from the system.

I recommend doing another test to check if the drain test has worked and everything is functioning well.

5. Replace the Negative Battery Cable

After you are sure that the parasitic draw has been resolved, you can then replace the battery cable with the negative terminal.

For some cars, you have to use the wrench again to make it tight and not easily removable. For the other cars, just replace the cable to the terminal and the cover.

Tests Compared

red multimeter

Although there are many tests for battery checks, I recommend using the multimeter method. This is because it is simple and easy to carry out even by yourself. The other method, using an amp clamp, is convenient for measuring small voltages across the batteries.

Because of this, it is better to use the multimeter since it measures a wide range of values from the range. Also, a multimeter is easier to get from hardware stores or online stores. (2)

Wrapping Up

If your car is having problems starting when you turn on the ignition key, then this is how you can check for yourself. I hope that this article to test battery drain with a multimeter has been helpful to you.

You may check other related articles below. Until our next one!






References
(1) online trusted source – https://guides.lib.jjay.cuny.edu/c.php?g=288333&p=1922574
(2) online stores – https://smallbusiness.chron.com/advantages-online-stores-store-owners-55599.html

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.