# 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.

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Andrew
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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

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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
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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

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Shawn
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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!

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