How to Test Your Car Battery with a Multimeter

How to Test Your Car Battery with a Multimeter

26th Sep 2017

If your car reluctant to start the first few times you turn the ignition? While it could be the starter, the most common cause of this phenomenon is the battery. A good battery should hold enough charge to start the car on the first turn, at which point the alternator will kick in. But like all automotive components, batteries die and must be replaced. So, how do you know if your battery is going bad?

The 4-Year Mark

Before we begin, it's important to note that most car batteries are designed to last for four years. When you purchase a new battery, the manufacturer may even give you a four-year warranty on it, meaning you can have it replaced if it fails prior to this time (keep your receipt). With that said, statistics show that only about a third of all car batteries reach the four year mark; the rest die before this period.

Testing Your Battery with a Multimeter

The easiest way to test your car battery is to use a multimeter. This device allows you to measure voltage, current and resistance. You can buy them for about $20 bucks, which is a small price to pay considering the versatility it offers. 

To test your battery, make sure your engine is turned off and pop your hood. Next, set your multimeter to 20 volts direct current (not alternating current). Your multimeter should have two probes: a red probe and a black probe. The red probe is for the positive terminal, and the black probe is for the negative terminal. However, the black probe should be connected to the port labeled "COM" on the multimeter, whereas the red probe should be connected to the port labeled "volts, ohms and milliamps." Don't connect the red probe to the port labeled "10A," as this may damage your multimeter.

With the probes connected to the multimeter, touch the tip of the black probe to the negative terminal on your car battery and the tip of the red probe to the positive terminal. Hold it for a few seconds while monitoring the display for voltage.  If your car battery is good, it should read 12.4 to 12.7 volts. If your car battery is only half charged, it will read 12.2 volts. Any reading below 12 volts is considered discharged and the battery must be replaced.

Of course, another way to test your battery is to take it to a local auto parts store, such as Auto Zone. Most auto parts stores will gladly test your battery and/or alternator.