How to Check the Voltage of a Car Battery

There are few things more frustrating than discovering that your car won’t start because the battery is dead. A mechanic can measure the voltage in the battery, in order to determine whether it needs to be replaced. There are two ways to do this.

Open circuit voltage test

This car battery test determines how fully charged your battery is. This test is done twelve hours after shutting off your car, so that any surface charge can dissipate. This means a more accurate reading. The test is done with the engine off. Then your mechanic may either use a multimeter/voltmeter, or a dedicated battery tester. The dedicated tester is simply connected to the battery terminals and the voltage can be read. With the multimeter, the device is configured to measure voltage up to 20 volts. Then the leads are connected to the battery terminals, positive to positive and negative to negative to get the voltage.

A reading of 12.65-12.77 volts means your battery has a full charge. 12.45-12.54 volts means you have a 75% charge, 12.24-12.29 is 50% charged, and 11.99-12.06 volts is 25% charged. 11.75-11.89 volts means your battery is dead.

Electrolyte gravity voltage test

This is the method used for non-sealed lead acid batteries. With this method, a hydrometer measures battery voltage. A specific gravity of 1.269 means that the battery is fully charged. A reading of 1.229 indicates a 75% charge, 1.194 is a 50% charge, and 1.159 is 25% charged. 1.124 means you have a dead battery.

Performance and capacity load test

This type of car battery test measures the ability of the battery to produce current. Before you do this test, YourMechanic will test the car battery to be sure that it has at least a 75% charge. Then, the voltage of the battery is measured under a load similar to what it takes to start your car. Then, he or she will use a dedicated load tester – it’s a large resistor, with a resistance much like your car’s starter, and a meter that shows the output voltage – to apply a load equivalent to ½ of the cold cranking ampere rating of the battery for approximately 15 seconds. You should expect a reading no lower than 9.1 volts.

Have your car battery tested regularly. You should have your car battery tested at least once a year, preferably when the cold weather begins.


Next Step

Schedule Car Battery Replacement

The most popular service booked by readers of this article is Car Battery Replacement. YourMechanic’s technicians bring the dealership to you by performing this job at your home or office 7-days a week between 7AM-9PM. We currently cover over 2,000 cities and have 100k+ 5-star reviews... LEARN MORE

SEE PRICING & SCHEDULING

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Recent Car Battery Replacement reviews

Excellent Rating

(9,922)

Rating Summary
9,614
183
41
20
64
9,614
183
41
20
64

Andrew

16 years of experience
657 reviews
Andrew
16 years of experience
Honda Civic L4-1.8L - Battery - Beaverton, Oregon
Andrew was amazing. He was kind, smart, and super friendly. Got the job done in no time and I'm very pleased with the work he has done. My car works again. Thank you, Andrew.
Ford Transit Connect - Battery - Portland, Oregon
10/10 would recommend and will book again if something comes up that isn't expressly dealer specific.

Lucas

30 years of experience
938 reviews
Lucas
30 years of experience
Kia Forte5 L4-2.0L - Battery - Van Nuys, California
Lucas was very professional and completed the work on my car quickly and efficiently. He communicated his arrival time with me so I knew exactly when he would get here. I would definitely request him again if I need work done in the future! Thanks Lucas!
Honda Accord - Car Battery Replacement - Sherman Oaks, California
Excellent! Replaced the battery, constantly examining the cables and connections. Cleaning off corrosion and dirt along the way. None of the "mystery" associated with brick and mortar mechanic shops - "customers are not allowed..." Ended with guidance to protect the the life of new battery life by operating the car more frequently than I do.

Attila

20 years of experience
1104 reviews
Attila
20 years of experience
Dodge Grand Caravan V6-3.3L - Battery - Cranford, New Jersey
This is the second time Attila has serviced my car. The car and extra mile that he takes is exceptional
Honda Civic - Car Battery Replacement - Jersey City, New Jersey
Great experience, very kind and gracious. Worked efficiently and smooth. Explained what he was doing and why which was very helpful. He deserves a raise if he isn’t already getting one. I would recommend his service to others if they need help.

Shawn

13 years of experience
379 reviews
Shawn
13 years of experience
Mercedes-Benz GLE350 V6-3.5L - Car Battery Replacement - Coatesville, Pennsylvania
Shawn was awesome! Super courteous and personable, showed up on time, got the job done and was very thorough checking everything out for us. Really appreciated the awesome job and knowledgeable service!

Need Help With Your Car?

Our certified mobile mechanics make house calls in over 2,000 U.S. cities. Fast, free online quotes for your car repair.

GET A QUOTE

Related articles

How to Buy a Battery for Your Car
Your Your car battery is a storage device for the electrical power you need to start your car and operate your car’s options. If your car battery isn’t working as it should, you may not be able to start your...
How to Buy RV Batteries
RV RV (recreational vehicle) batteries come in many different types, and what type is best depends on the useage and conditions the RV (https://www.yourmechanic.com/article/5-essential-things-to-know-about-owning-an-rv) will be exposed to. Unlike cars, RV’s use multiple batteries. These batteries are used to power...
Electric Cars and How They Work
Electric cars use an electric motor driven by a control unit. Their batteries are filled at charging stations and they produce no tailpipe emissions.

Related questions

Battery going dead on a 2003 Honda Odyssey
Yes, it certainly could be. Of course, the first thing you'd want to do is have any good mechanic check your battery and your alternator. There is a load-test that the mechanic can do; YourMechanic guys can do it and...
Car is not starting and new battery didn't work
Hello. It sounds like the battery fuse (https://www.yourmechanic.com/services/fuse-replacement) may have blown out. The battery fuse is a high amp fuse that can range from 80-amps to 120-amps, and is bolted to the fuse box. It also sounds like there may...
Car wont start and electronics acting up
As long as no water has gotten into the car, sight unseen I would suggest checking for loose connections. Positive and negative battery cables (https://www.yourmechanic.com/services/battery-cable-replacement), not just at the battery. Check the other ends - where the positive cable connects...

How can we help?

Our service team is available 7 days a week, Monday - Friday from 6 AM to 5 PM PST, Saturday - Sunday 7 AM - 4 PM PST.

1 (855) 347-2779 · hi@yourmechanic.com