How to Test a Car Battery

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How to Test a Car Battery Safely and Make Sure It’s Within the Right Parameters

Do you want to figure out exactly how to test a car battery safely and without any hassle? There are several different approaches you can take in order to achieve this task, and none of them are too difficult. Testing your battery can be essential, especially when the battery is old and worn out, and you want to avoid having to deal with jump starting your car at inconvenient times or having your battery die on you in the middle of the highway. However, experts recommend that drivers test their batteries twice a year in order to avoid any chance of failure in time.

Preparation Requirements Prior to Testing

Before considering how to test a car battery using the most common means, you have to keep track of a few important preparation tasks. Start by turning your car off and turning off all the lights. Also, turn off any other electric or electronic device that might use battery power without the ignition on. Next, you can continue by turning your ignition off, however, it’s also a good practice to temporarily disconnect your entire ignition system by removing the fuel pump relay or fuse, or by simply uncoupling the ignition coil (if your car is equipped with a coil, distributor and plug wires).

Check for “Dead” Battery Terminals

Although knowing how to test a car battery is an important skill, when dealing with a seemingly dead battery, the problem might simply be in the terminals. To do this, with the ignition system disabled, start by touching your multimeter’s red probe to the battery’s positive terminal, then the black probe to the terminal that connects through the cable to the same battery terminal. Then ask someone to assist you by cranking up the engine. In that moment, if the multimeter registers more than .5 volts, it means you most likely have to clean the clamps or replace the cable connecting the battery to your car. Repeat the process with the other battery terminal, but this time switching the probes to connect the black probe to the battery terminal. If you see fluffy or powdery greenish-white deposits around the terminals, it could well just mean that corrosion has built up to a point where it’s preventing the battery from receiving or delivering a charge.

Testing Your Battery with a Multimeter

Even if you’re not used to the idea of using a multimeter, you’ll find that the process of checking your battery using the multimeter is, in fact, fairly simple. Begin by removing the battery’s positive terminal cover, then clean it to remove any corrosion. Set your voltmeter to the lowest voltage setting that’s above 15 volts, then connect the negative lead to the negative battery terminal and the red lead to the positive terminal. This is essentially the whole process, and now you simply have to know what voltage to expect from your battery.

How to Test the Battery with a Power Probe

Have you ever tried figuring out how to test a car battery with a power probe? A somewhat more simple process, connecting the power probe ensures that you don’t need to adjust any settings as you did with the multimeter. The process is the same in the beginning; you simply have to taking off the battery’s positive terminal cover, then connect the probe’s connective leads – positive to positive and negative to negative. Once you’re done, the power probe should already show you whether or not your battery is in good condition.

How Many Volts Should the Battery Carry?

Depending on whether the battery is currently charging or not, the value you read on the voltmeter might vary. If you performed all the steps as above, using either a multimeter or a power probe, you should get a reading between 12.4 and 12.7 volts. Anything lower than 12.2V or higher than 12.9V means your battery either needs a slow charge, or the removal of excess charge. You can achieve the latter option by temporarily connecting the high beams. The exception is when the alternator is charging the battery, in which case you should see a value of about 14.5 volts. As you can see, learning how to test a car battery can be fairly easy, as long as you follow all the steps closely.

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Last updated December 12, 2017

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