Are Car Battery Testers Accurate?
Voltmeters and multimeters let you test the health of your car’s battery. However, they’re not always 100% accurate.
They’ll give you an accurate measurement of the battery’s voltage, most of the time.
Most digital battery testers are largely accurate with an expected accuracy of plus or minus 0.5% when testing a car battery. By comparison, analog battery testers have an accuracy range of plus or minus 3%.
A battery can have plenty of volts and still not work, though. If it has too much internal resistance, it won’t be able to crank the car.
How Accurate Are Car Battery Testers?
Measuring the accuracy of a battery tester isn’t always easy. Most of them display results using a relative measurement, instead of absolute.
That means it can tell you the difference in electrical potential between objects.
However, they’re not always able to measure the electrical potential of an object. High-quality battery testers are usually more accurate than cheaper models.
We can also describe battery testers by looking at their resolution. Some of them are able to measure small units of electrical potential, like 1 mV.
Not all of them have the ability to measure units that small, though.
A lot of digital multimeters have settings where you can adjust their resolution. So, you can set them to measure small units if you’d like them to.
You’ll get better results if you’re using a digital multimeter. They’ve designed them to be more accurate than their analog counterparts.
n analog multimeter has an accuracy rate of /- 3%.
So, you can expect an analog multimeter to give you something within 3% of the actual result.
Most digital ones can give you a result that’s within 0.5% of the actual result, though.
Can Battery Testers Be Wrong?
The accuracy of your battery tester’s measurements depends on what you’re measuring. If you’re measuring something that’s high-voltage, it’ll be less accurate.
The more power you’re measuring, the less accurate it’ll be.
Another factor that can impact your equipment’s accuracy is how long it’s been used.
Using a battery tester tends to make it drift out of calibration over time. You may need to recalibrate your device if you’ve used it a lot.
You may not be testing the battery properly, either. You’ve got to test them properly if you’d like to get accurate results.
If you’re using a digital multimeter, it’s not hard. Set it to DCV. This setting lets you measure a circuit’s voltage.
Take the multimeter’s positive probe and touch the battery’s positive terminal. Touch the negative terminal with the negative probe while holding the other one in place.
After you’ve touched both probes to the battery, your multimeter should light up. You should see a reading on its screen that tells you how many volts the battery is making.
A good battery should produce more than 12 volts. Many of them produce over 14 volts whenever they’re fully charged.
If it’s not making that many, it’s not going to work. Less than 12 volts isn’t enough to crank the engine on most cars, nowadays.
You can also try to test the battery’s amps by using the appropriate setting on the multimeter. However, that’s not always going to tell you whether your car will work.
Testing its amps can tell how much charge the battery has after you’ve disconnected it from a charger.
Most batteries have a label on them that tells you how many cold-cranking amps they have.
You should be able to test the battery’s amps and compare its results to what’s on the label. It should produce however many amps it has on the label after it’s finished charging.
Using the proper technique should minimize most inaccuracies. But, you should always use high-quality equipment to conduct your tests. They’ll give you more accurate results than using something that’s cheap.
Make sure to set your multimeter to the appropriate setting if you’re testing the battery, too.
Trying to measure a battery’s potential in KV wouldn’t be useful. Always use millivolts when you’re testing one of them to get the most accurate results.
Can a Car Battery Test Good but Still Be Bad?
If you’ve tested a battery’s voltage, but it’s still not working, resistance may be a problem. A battery can have enough volts to crank a car and still have issues doing it.
When you’ve used a battery for a while, resistance begins building within its cells. All batteries have a limited number of charges, called their cycle life.
You can only use them so much before they’re no longer able to hold a charge.
Testing the battery’s voltage could give you a reading that’s above 12 volts.
But, you might not be able to crank the car if you’ve got it in the engine bay. That’s because the battery’s circuits have too much resistance in them.
You can actually test the battery’s resistance by using a multimeter. Set yours to the resistance setting and use it to check the battery. The more ohms it has, the more resistance there is.
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Using a multimeter is one of the most common ways to test your car battery.
You can grab one at your local hardware store for less than 10.
Some other car battery tester tools, like a voltmeter or power probe, can also get the job done. However, a multimeter is your best bet since both a voltmeter and a power probe are more limited in their capabilities to test battery performance.
The process is quite simple, just follow these steps:
However, before testing your battery with a multimeter or any other car battery tester, there are a few things to remember.
These instructions are for what’s referred to as maintenance-free batteries. These batteries don’t have plastic caps on each cell. If you have a battery with plastic caps, you will need a hydrometer to test it, not a multimeter.
Always wear rubber gloves and goggles when working on your battery. This will protect your skin and eyes from battery acid.
With that taken care of, let’s get into how you can start testing your battery life:
Step 1. Remove The Surface Charge From The Battery
To do this, turn your headlights on for about two minutes. Don’t turn the car on, just the headlights. We do this because we need to test the battery’s resting voltage; otherwise, you can get a false reading, as the battery might still be holding a charge from the alternator.
Step 2. Perform A Quick Visual Inspection
While you’re waiting with the headlights on, you can go ahead and give the battery a quick visual inspection. You want to look out for any corrosion buildup which could be affecting your battery performance.
It usually looks like a white or yellow crust that forms around your battery terminals. Corrosion might even explain why you’re having battery issues in the first place.
If you see some corrosion, you can clean that off with a battery-cleaning solution, like baking soda and water or some fine sandpaper. Read this guide for instructions on safely removing corrosion from your battery.
While you’re there, double-check that you fastened each battery cable correctly.
If everything looks alright, move ahead to the next step.
Step 3. Set Up Your Multimeter
Now that you’ve prepared the battery, you can start setting up your digital multimeter to test your batterys voltage.
To do this, adjust it to about 20V DC volts. Setting it to 20V isn’t a must; the important thing is that it’s above 15V DC volts, so you get the correct reading. You can go ahead and turn your headlights off.
Step 4. Connect The Multimeter
First, connect the negative cable (black) on the multimeter to the negative terminal on the battery. Then connect the positive point (red) on the multimeter to the positive terminal on the battery.
Step 5. Check The Multimeter’s Display
When connected to a fully charged battery, the multimeter will highlight your car battery voltage as being between 12.5V to 12.6V if everything is working as it should be.
Remember, the outside temperature and your battery type affect your batterys voltage.
- For a standard lead acid battery at around 80℉ (27℃), a good battery that’s fully charged will be in the 12.2 – 12.6 volt range. Whereas a fully charged AGM battery will have an open circuit voltage of about 12.8V to 12.9V.
- At 30℉ (-1℃), the battery voltage will be around 12.58V and 12.51V.
- At 0℉ (-17℃), your volt reading will be slightly less if you have a good battery.
For reference, a lead acid battery that’s about 75% charged will have a volt reading of around 12.45V. Anything below 12V suggests something is wrong with your battery and probably won’t start your car.
If the multimeter displays the battery’s voltage as anything between 12.3V and 12.5V, it could use a charge. If it doesn’t start, you can jump-start your car from someone else’s with a pair of jumper cables. Once your vehicle is running, the alternator can charge your battery. Alternatively, a battery charger suited to your car battery type will also work.
Anything below 12.2V suggests the battery’s resting voltage is weak, and you’ll need a replacement.
Tip: Owning a working set of jumper cables is a must. Of course, knowing how to use them is also vital.
Step 6. Turn On Your Car
Have someone else turn the car on while the digital multimeter is still attached.
The voltage reading should change, but the voltage drop shouldn’t go below 10V. If it does, your battery isn’t producing the correct voltage to power your car.
How To Test A Car Battery Without A Multimeter
While performing battery testing, although a multimeter is the most efficient method, it’s not the only method.
If you don’t have a digital multimeter or another type of battery tester on hand, there are a few things to help figure out how your battery is performing.
Perform A Quick Visual Inspection
Ensure the battery isn’t leaking and it’s not bulging — your battery case should be a perfectly square box. Also, look for corrosion around your battery terminals and ensure that each battery cable is connected securely.
If everything seems fine, move to the next step.
Test The Battery
Start by turning your car off and switching the headlights on. Leave them on for about 15 minutes.
Crank The Engine
After waiting around 15 minutes with the headlights on, crank the engine and see what happens. You’ll probably need some help here so you can keep an eye on each headlight. You might see your headlight dim slightly as you start your car; this is normal.
However, there are a few things that suggest you have a problem with your charging system:
- Your headlight gets much dimmer or turns off entirely
- The engine takes a while to turn over
- There’s a clicking noise
Remember that this isn’t nearly as accurate as using a digital multimeter, but you can use it to tell if your battery is performing as it should.
If your car turns on fine and the headlights aren’t dimming, your charging system is probably functioning normally.
Having said all of that, how do you tell if you have a bad battery?
Signs Of A Bad Battery
Generally, you should conduct a car battery voltage test about twice a year to avoid total battery failure. However, there are several other signs to look out for to help prevent a dead car battery. If these symptoms appear, don’t wait for routine car maintenance to get your battery checked:
Slow Engine Starting
This is often the first sign of battery failure.
When something’s wrong, your battery will struggle to hold a full charge, which often manifests as a slow engine start.
The main reason for this is the battery not sending enough power to the starter motor to get the engine to turn over. If this is a common issue for you, there’s a good chance you’ll have a dead car battery fairly soon.
Dim Lights
As mentioned above, dimming lights is another good indicator of something wrong with your battery, though this also refers to your interior lights.
For example, you may also notice issues with another electrical component, like the power Windows or radio. An electrical component like this is more likely to fail altogether, while your lights will start dimming before they fail outright.
A Clicking Noise
If your battery can’t send enough power to the starter motor to turn your car on, you’ll likely hear a series of clicks. This will tell you that you have a dead battery and your car won’t start.
Battery Light On Your Dash
You may notice a battery indicator light on your dashboard when your battery starts acting up. Some cars will throw up a general check engine light, whereas others may show an image of a battery.
If that light is on in your dash and you’re noticing a few other symptoms, it’s a safe bet you’re dealing with battery failure, and you’ll probably need a battery replacement.
Now let’s look at some FAQs to give you a better understanding of your car battery.
Our Top Picks
Armed with some solid background on the best battery testers, you’re ready to start shopping for the right model to suit your needs. Ahead, review a host of options considered among the best battery testers on the market. Be sure to keep the top considerations in mind when comparing products.
Topdon 12V ArtiBattery101 Car Battery Tester
Those looking to keep tabs on a vehicle’s 12-volt battery system should check out the Topdon ArtiBattery101 car battery tester. Small and light, this handheld digital battery tester features a large, easy-to-read screen and provides menu text in English, Russian, Spanish, French, German, and Italian, making it one of the best car battery testers on our list.
This tester is compatible with most 12-volt systems, including wet cell, gel, and AGM, so it can be used for cars, trucks, boats, and most modern motorcycles. It provides readings during static state, charging, and cranking, allowing users insight on battery condition at all times. Topdon’s ArtiBattery101 also includes two leads with alligator-style clips for clipping on the battery terminals and connections for hands-free testing.
Product Specs
- Type: Digital
- Compatible battery type(s): Wet cell, gel, and AGM
- Ease of use: Easy
- Compact and lightweight with large screen that’s easy to read while checking battery power
- Includes 6 preprogrammed languages: English, Russian, Spanish, French, Italian, and German
- Suitable for cars, SUVs, boats, trucks, and motorcycles; provides readings while static, charging, and cranking
Get the Topdon digital battery tester at Amazon or Newegg.
Ancel 12V BST200 Car Battery Tester
As a simple, quality digital battery tester that comfortably fits in the palm of the hand, the Ancel BST200 car battery tester deserves a look. This 12-volt battery tester is compatible with most systems, including wet cell, AGM, and gel, allowing the user to check the condition of batteries in lawn equipment as well as cars, trucks, boats, motorcycles, and RVs.
This digital model has a large display that’s easy to read and understand, with a simple four-button control pad. It has two permanently attached alligator-style clips, allowing users to clip the leads to the battery terminal for hands-free testing. Also, this unit has two testing modes, including in-car and out-of-car, to provide a reading whether the battery is disconnected or if it’s tied into the electrical system.
Product Specs
- Type: Digital
- Compatible battery type(s): Wet cell, AGM, and gel
- Ease of use: Easy
- Compact and lightweight with simple 4-button control pad and large display for easy reading
- Includes 10 preprogrammed languages: English, Spanish, French, German, Dutch, Italian, Portuguese, Polish, Turkish, and Russian
- 2 testing modes (in-car and out-of-car) provide user more accurate data
- A bit more expensive than other car battery testers on the market
- Should not be connected to a battery over 18 volts
Get the Ancel BST200 battery tester at Amazon or Newegg.
D-FantiX 9V BT-168 Battery Tester
Anyone with a junk drawer full of loose batteries might want to check out this D-FantiX battery tester. Considered the best small battery tester, this affordable battery tester is compatible with small batteries, such as AA, AAA, C, D, and 9-volt which means this is also one of the best home battery testers we have on our list. Though an analog unit, the gauges are easily read and understood, with red, yellow, and green indicating battery health.
To test 1.5-volt batteries on the D-FantiX battery tester, simply slide the handle back and place the battery between the contacts; testing 9-volt batteries requires touching the contact to the appropriate points on top of the unit.
Jump to Our Top Picks
Staying on top of battery health can ensure that power equipment, vehicle, or even video-game controllers are working properly. Plus, these devices are more versatile than their name implies, as they can do more than just test voltage. The following sections point out the most critical factors to consider when choosing the best battery tester.
Types of Battery Testers
The two main types of battery testers, digital and analog, differ in the way they deliver information to the user.
- Digital battery testers feature LCD displays that provide clear, accurate, easy-to-understand readings. Typically, users can switch between settings for static, cranking, and charging tests with a button. While digital models don’t boast new technology, they’re much more advanced than their analog counterparts.
- Analog battery testers can be harder to read than digital models. They have a needle that rises and falls across a printed gauge, indicating the power level in the battery. The gauge is fairly small and has hash marks as well as numbers, so the reading may be less precise than with a digital tester. Also keep in mind that some analog testers do not have their own on-board batteries, so if the battery being tested is dead, none of the features will work.
Battery Type
It’s important to know what kind of battery you’ll be testing, since not all testers are compatible with every kind of battery. Battery types include wet or flood cell, cylindrical, AGM (absorbed glass mat), gel cell, spiral wound, deep cycle, and more—designations that refer to the chemical makeup or construction of the battery.
Also, batteries vary in the voltage they produce. Smaller batteries, such as AA, AAA, C, and D, produce only 1.5 volts. These batteries don’t produce enough electrical signal for some battery testers, so testers designed for lower voltage are necessary. The units that can test these lower-voltage batteries typically don’t require leads, which are electrical contact points on the end of a wire.
Batteries found in older lawn equipment, small power tools, and some older motorcycles produce 6 volts, while larger vehicles such as cars and trucks use 12 volts. Both of these battery types require leads for testing.
Ease of Use
Most battery testers are straightforward tools, but overly large, clunky models can be tedious to set up. Also, models with small gauges or tiny digital readouts can be difficult to read. The best battery tester will have a large gauge that’s easy to read quickly and accurately. A quality digital model will also feature straightforward buttons and control pads.
For smaller batteries, one-hand use can make testing a much faster process. For larger batteries, clip-on leads can make a huge difference, especially when going for accurate readings during cranking.
Connector Leads
The best battery testers designed for larger batteries require leads, the electrical contact points on the end of a wire. One lead goes to the negative side of the battery, while the other goes to the positive side. As the energy from the battery passes through the leads, it registers a reading on the tester.
The leads on battery testers typically come in two types: points and clips. Points will do the trick, but clips attach the leads securely to the battery so the user can FOCUS on the readings. This can be a big help, particularly while testing batteries in larger vehicles with complex electrical systems.
Types of Readings and Modes
Vehicle battery testers differ from multimeters in that they take different types of readings. They can take static readings when the battery isn’t connected to the car, load readings when it is connected, and readings during cranking and charging cycles.
With most digital models, users can hook these battery testers to the terminals, set it to the correct setting, place it on a surface, and then board the vehicle and crank the ignition. The battery will take all the readings and display them when the user gets out to review them.
Many testers also have settings for “in car” and “out of car” readings, which can be helpful for determining parasitic draw (when the vehicle drains the battery, even when it’s off).
Anti-Slip
While testing the batteries in larger vehicles, users must often place the unit down on the vehicle. Whether it’s on top of the battery, on the edge of the fender, or on top of an air cleaner, putting the tester down allows the user to manipulate the leads with both hands. If the tester doesn’t have a grippy surface, it can slide off and become damaged. So a rubber anti-slip surface is helpful when testing vehicles. Some models feature rubber covers, while others might have a strip of rubber across the back.
FAQs
Still have a few more questions surging through your mind? Check out the answers to some common queries about battery testers.
Q. How accurate are battery load testers?
Battery testers are relatively simple tools, so accuracy is rarely an issue. Digital models are highly accurate, while the gauges in an analog tester might be harder to read with the same pinpoint accuracy.
Q. How do I test a battery to see if it’s good?
To test a battery, either place it in the appropriate slot in the tester or press the leads to the terminals of the battery. Analog models should provide a reading right away. Digital models might have a few menu prompts to follow before getting a reading.
Q. How long will my battery tester last?
Battery testers are relatively simple tools, so it’s not unreasonable to expect 10 years of service from a quality model. Do keep in mind that most testers run on a battery, which typically needs to be changed once each year.
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Load Test the Battery
If the battery’s state-of-charge is at 75 percent or higher or has a good built-in hydrometer indication, then you can load test a car battery by one of the following methods:
- With a battery load tester, apply a load equal to one-half of the CCA rating of the battery for 15 seconds. (Recommended method).
- With a battery load tester, apply a load equal to one-half the vehicle’s CCA specification for 15 seconds.
- Disable the ignition and turn the engine over for 15 seconds with the starter motor.
During the load test, the voltage on a good battery will NOT drop below the following table’s indicated voltage for the electrolyte at the temperatures shown:
Load Test
If the battery is fully charged or has a good built-in hydrometer indication, then you can test the capacity of a deep cycle battery by applying a known load and measuring the time it takes to discharge the battery until measures 10.5 volts. Normally a discharge rate that will discharge a battery in 20 hours can is used.
For example, if you have an 80 ampere-hour rated battery, then an average load of four amps would discharge the battery in approximately 20 hours. Some new batteries can take up to 50 charge/discharge preconditioning cycles before they reach their rated capacity. Depending on your application, fully charged batteries with 80 percent or less of their original rated capacity available are considered to be bad.
Bounce Back Test the Battery
If the battery has not passed the load test, remove the load, wait ten minutes, and measure the state-of-charge. If the battery bounces back to less than 75 percent state-of-charge (1.225 specific gravity or 12.45 VDC), then recharge the battery and load test again. If the battery fails the load test a second time or bounces back to less than 75 percent state-of-charge, then replace the battery because it lacks the necessary CCA capacity.
If the battery passes the load test, you should recharge it as soon as possible to prevent lead sulfation and to restore it to peak performance.
