Skip to main content

How to Test Car Battery Charger With Multimeter

Fernando the electronics guy is an electronics engineer. He earned his Bachelor of Science in Electrical Engineering from UC Riverside.

Test Car Battery With Multimeter the right way. Have the best tools.

Test Car Battery With Multimeter the right way. Have the best tools.

Trying to figure out how to test car battery with multimeter? You're not alone. This is usually one of the hardest places to start when you don't understand electricity very well. You don't need to have the best tools. But, you simply need to know some electricity basics. Here, we will show you everything you need to know. All without making you throw up.

How to Test Car Battery Charger With Multimeter: The Basics

As shown above, electrical current travels from the battery to the light bult (from positive post on battery). It does it's job, and returns back to the battery (to negative post).

In essence, electrical current flows from positive to negative. It leaves home to later return back to where it came from. Kind of like when we leave our homes to go do a job. We then return back when we are finished (we're tired).

A lot of confusion erupts because there's a lot of correct information on the internet without a reason why. For example, although we did say electric current flows from positive to negative, electrons are negatively charged. As a result, negative electrons flow from negative to positive.

But, here's where a lot of people get confused: they're both describing the same thing. Yes, I said it. Positive to negative or negative to positive? It doesn't matter. It's all about what makes you feel better.

So, in essence, you either care about holes or carriers, electrons or current. When it comes to multimeters, it ends up we tend to use the positive to negative convention.

Multimeter Features

Now that you understand we're measuring from positive to negative, it's important to familiarize yourself with a few modes found on the multimeter.

  • DC voltage measurement. Direct current mode. In this mode, you'll be measuring direct current. This mode is great for measuring voltage that is steady and constant. Your car battery, for example, is 12 volts DC. This distinction is important. Also, DC voltage and AC voltage measurements both don't allow electricity to pass through it. Instead, the multimeter is comparing the voltage between the positive and negative probes. So, it's extremely safe.
  • AC voltage measurement. If you're trying to measure an automotive battery, this isn't the place for you. If you're trying to measure how the alternator is doing from the automotive battery, this might work. The AC voltage measurement is all about waves. A constant value may not be picked up by this measurement technique. Your house electricity, for example, runs off of AC voltage. Your car battery does not.
  • Ammeter mode. This mode is for when you want to measure the current draw. You cannot measure voltage from here. In fact, I highly suggest you never use this mode unless you know what you're doing. If you don't know what you're doing, electricity will pass through your multimeter as if it was a light bult (best way to explain it). Don't try this at home.
  • Ohmmeter mode. When you're trying to check resistance of a system, this is the place to be. A resistance of zero equates to a short circuit. A resistance around the mega (M, capital M) means approaching an open circuit.
  • Continuity mode. As mentioned before, high resistance equates to an implied open circuit (no sound in this mode). A low resistance equates to an implied short circuit (beep). This is the mode you want to be in when you want to find out if there is continuity between two points. Follow the beeps. If there are no beeps, there is no continuity (no two metals are touching). This is great for diagnostics.
  • Etc. Check your multimeter's manual for further modes not included in this list.

How to Assemble Your Multimeter

First, it's important to note that you won't be shocking yourself if you do this right.

1. Grab your multimeter.

Scroll to Continue

2. Identify the positive probe. It's red.

3. Identify the negative probe. It's black or green.

4. Turn on multimeter. Make sure it's in DC voltage mode. It's supposed to have a sign that looks something like this: ---||---. If you're in a mode that looks like ---~---, this is AC mode. You don't want to be there. Even worse, don't be in ampere mode (measured in A). If you're in this mode, you'll spark something. DC mode is perfectly safe. There will be no sparks. Be careful to ensure this.

5. Place positive probe inside red hole. Place negative probe inside black hole.

6. With red positive probe, touch positive (+) terminal of battery. At the same time, with black negative probe, touch negative (-) terminal of battery.

7. Read your screen's reading.

Once you've followed the top steps, read the voltage reading. If it reads above 12 volts, you're good to go. If it reads below 12 volts, you need to charge your battery.

How to Test Car Battery Charger With Multimeter: The Final Step

Now, go ahead and turn on your car.

Check the voltage.

If the voltage is above 13 volts, your charging system is working properly. The charging system is composed of the alternator and its full-bridge rectifier diodes.

If it is below 13 volts, there is something wrong with the alternator and the system will need checking.

This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.

© 2022 electronicsguy

Related Articles