How To: Test a Car Battery With a Multimeter?
- by Joe Weber - updated on 1/19/2024
Your car or truck's battery is the heart of your vehicle. Without it, you may as well walk or ride a bike everywhere. It is one of the few things in your vehicle where if it is bad or not functioning, the vehicle won't work.
Knowing when your battery is on its way out the door is tremendously helpful. Learn how you can test your car battery yourself at home by reading below.
Before You Begin
A car battery is packed with a lot of energy, so safety is extremely important. Before you even open the hood, turn on the ignition to make sure your car starts as normal. Then, with the engine running, make sure your headlights and any other lights are switched off. Also, make sure to turn off any other accessories, such as the radio, air conditioning, GPS and so on.
Switch off or unplug any devices that can still run with the engine off: you don't want any electricity flowing through the system at all for the test to be accurate. Once you've done all this, shut the engine off.
Finally, since lead acid batteries contain dangerously corrosive materials, it's a good idea to wear protective eyewear and sturdy, waterproof gloves to protect you if the battery has a leak or other problem.
How To Test A Car Battery Voltage
The easiest way to test your battery is by using a common electrical multimeter, available at many hardware and home improvement stores nationwide. While this may be a little daunting if you've never done it before, it's a straightforward thing to do.
Step 1
Set the multimeter to a low setting where it can accurately measure around 15 volts of direct current (DC).
Step 2
Make sure the engine is off. Pop the hood and remove the cover from the battery's positive terminal.
Step 3
Remove any corrosion or grease and clean the positive terminal to ensure good electrical contact with the multimeter.
Step 4
Do the same with the negative terminal.
Step 5
Connect the multimeter to both terminals, with the red lead going to the positive and the black to the negative.
Test Results
The moment you connect both leads to the battery you will see a reading on the multimeter's display.
- Seeing a reading between 12.4V and 12.7V shows a healthy battery carrying a good charge.
- If the voltage is reading below 12.2V, it likely needs a recharge to bring it back up to an acceptable level or it may need to be replaced.
- Either use an appropriate automatic charger or take a drive on the highway for 15-30 minutes to let the alternator charge the battery in less severe cases. Retest using the process above to see if the reading has changed.
- If it's reading higher than 12.9V, the battery is overcharged and needs the extra energy removed to prevent long-term damage.
- You can do this by switching your headlights onto the high beam setting until the voltage is back inside the ideal range. Just remember to turn them off after the voltage drops so you don't cause your battery to drain.
Is My Battery Bad if It Doesn't Have High Enough Voltage?
A low reading doesn't necessarily mean your battery is bad or dead, but if it remains low after attempting to recharge or by taking a highway drive, it's a good idea to have it checked out by an expert at your local Batteries Plus.
Check the Voltage Again with the Vehicle Running
Use the multimeter to assess the battery's voltage once more, but this time while the vehicle's engine is running. This step verifies whether the alternator is generating the appropriate charging voltage during driving, ensuring the battery remains charged. The recommended voltage reading should hover around 14V, typically falling between 13.8V and 14.5V.
Can Batteries Plus Test My Battery?
Testing a car battery with a multimeter is pretty straightforward but we realize that it's not something everyone has the tools to do or will want to do. As an alternative, simply bring your car to your nearest Batteries Plus store and we can test it for you, completely free of charge.
Having your battery professionally tested will not only test the battery voltage and the alternator functionality, but it will also test for Cold Cranking Amps (CCA) and simulate a load on the battery to really determine whether the battery is good, bad or on the verge of needing a replacement.
If your vehicle needs a new battery we can help you find the right replacement no matter what power demands your car or truck has. We'll even make sure your old battery is recycled properly.