How To Test Your Car Battery With A Multimeter?
In this guide, we’ll tell how to test a car battery with a multimeter easily, both for the voltage and to load test it. You’ll also learn what a multimeter is, the symptoms to look out for to know you’ll need to use one to check your battery, and more.
Odds are, we’ve all been in this situation: tried to turn the ignition on, and been greeted with a whole lot of nothing – only the battery light lit-up on your dashboard, telling you your battery’s dead. Or maybe your headlights are dim, or your engine’s cranking when you start your engine.
All of these are symptoms of a dead or bad battery – and that’s something you need to check. Even more so during winter if you aren’t using the best car batteries for cold weather which you can find here.
Thankfully, instead of rushing out to buy a new battery or calling a mechanic, there’s a quick and simple way to check the power in your battery, by using a multimeter.
What is a multimeter?
A multimeter is a great little tool that can be found in most hardware stores – the shopkeeper can help you determine the best car battery tester for you. These reasonably-priced battery testers check the voltage of your car battery, and can tell you how much power you have left in it – indicating whether it needs charging, maintenance, or replacing.
How will I know if my car battery needs testing?
There are a few clear warning signs that will tell you that your car battery needs testing:
- Your dashboard and lights turn on, but your car won’t start.
- The battery light on your dashboard is illuminated.
- Your headlights are dim.
- You hear a crank, hum, or click when you start the engine.
- Your car won’t start.
- Your car needs frequent jump-starting with jumper cables.
If you find that any of these is the case with your vehicle, chances are your battery needs testing with a multimeter to figure out whether it’s working correctly.
Okay, how do you test a car battery?
Step 1: Turn The Ignition Off
First, make sure your car’s ignition is switched off so that you can work with the battery safely and accurately.
Step 2: Locate Your Battery
Pop the hood of your car and find the battery. It’s usually in the engine section of your car, but it could be in the trunk or under a seat.
Step 3: Set Your Multimeter
Take your multimeter and set it to the DC voltage setting, and then make sure that it’s set to 20 volts.
Step 4: Connect Your Probes
Plug the cables (also called test leads) that came with your multimeter into the two ports on either side or top of your device. The red cable should go in the positive port, and the black cable in the negative – make sure you double-check in your multimeter’s instruction manual about this, though.
Next, take the other ends of the leads (called the probes) and connect the red cable to the positive terminal of your battery, and the black cable to the negative terminal.
Step 5: Turn On Your Headlights
Next, turn on your headlights (if you’re holding the probes to the terminals, you’ll likely need someone helping you with this!).
Step 6: Measure Your Reading
Check the reading on the multimeter of your battery. Write it down and compare it with the below:
- A fully-charged battery will read at around 12.5-12.6 volts – ideally, ever so slightly above that. If your battery’s reading at this, it’s operational and your issues may be coming from somewhere else in your car.
- If your battery’s reading above 12.4 volts, it’s 75% charged and will still have some life in it.
- If your battery’s reading between 12.05-12.4 volts, it’s between 25%-50% charged and will need recharging fully.
- If your battery is below 12 volts, it’s discharged and will need further attention.
And that’s it!
As you can see here, testing a car battery with a multimeter is quick and easy, and will help diagnose your battery’s health in no time.
Battery Load Tester: How to Load Testing Your Battery
A multimeter can also act as a battery load tester. Performing a load test on your battery can help determine whether your battery’s functioning properly beyond whether it has the right voltage.
To perform a load test, fully charge your car battery, and then connect your multimeter to your car battery as shown above, with the car engine switched off. Set your multimeter reading to 20 volts and take down your battery’s voltage.
Then, turn your car engine on, and check how much your battery’s voltage drops. If your battery drops by less than two volts (for example, to 12.6 to 10.8), the battery’s still good to go.
If, however, your car battery drops by more than two volts or goes under 9.5 volts, the battery’s not in good shape and may need replacing.
Frequently asked questions
How Long Do Car Batteries Last?
With proper maintenance, most car batteries are traditionally meant to last between 4-5 years before they need replacing – however, for various reasons, batteries can often become obsolete much before that.
One brilliant way of extending the life of your battery and bringing it back to health is through a simple reconditioning process. Reconditioning your car battery can add up to an extra year of life onto it, saving you time and money. Check out our Battery Reconditioning Guide for more.
How Many Volts Should My Battery Ideally Have?
Ideally, your battery will read at 12.5 volts or higher – this indicates that the battery’s at a full or near-full charge. If you haven’t used your car for a while though, the voltage of your battery can lower – so if you haven’t driven it for a while, that could be why instead of it being faulty. In this case, charge your battery using a trickle charger.
Why Does My Battery Keep On Dying?
There are many reasons why a battery could keep on dying aside from it being faulty or inadvertently leaving the headlights on. It’s useful to check your car when it’s switched off to see if any systems in your car could be causing a parasitic discharge – ie., that are draining your battery without you knowing. Suspects for this include appliances plugged into the 12-volt outlet, amplifiers, plug-in stereos, or power seats.
It’s important to check your battery regularly to make sure it’s staying in good health. If your battery is showing signs of corrosion around its terminals, unplugging it and cleaning it with a solution of baking soda and distilled water with a toothbrush can help get rid of any build-up that could harm your battery over time.
Learning how to test a battery with a multimeter is quick and simple – and once you know how to use it, you’ll be able to diagnose problems with your car battery easily, helping you get back on the road again.
All batteries need correct maintenance – and one way of maintaining your battery can save you up to thousands of dollars in the long run. By reconditioning your car battery, you’ll be able to extend your battery life way beyond the projected lifespan of the battery. Check out EZ Battery Reconditioning to learn more about this incredible technique.