Vehicle Warranty Blog

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How to Test a Car BatteryEven if a car’s battery dies, that doesn’t mean it’s on its last legs. The lights may have been left on, or an accessory could be drawing too much power. However, on the opposite end of things, a battery that is still operating is not necessarily healthy, and it could even be nearing the end of its operational life, unbeknownst to you.

With that said, here’s what you can do to see where your battery stands:

Performing a Battery Test

Although testing is possible without any equipment, you should take readings with a digital multimeter for the best and most accurate results. A multimeter is a device that reads electrical values, such as volts, amps, or ohms, and fortunately, it will be the only major tool you need for the test. Still, you may want to have some gloves, baking soda, paper towels, and sandpaper on standby in case your battery terminals are corroded.

1. Set the Multimeter

Turn your multimeter to 20V DC before making any connections.

2. Prepare the Battery

Without turning on the car, leave the headlights on for two minutes to establish the battery’s resting voltage.

Next, examine the battery terminals for corrosion, a yellow or white crust. Thankfully, you can easily clean corrosion with a baking soda and water solution — just make sure to wear gloves. Remove any excess solution with some paper towels, and use sandpaper for particularly stubborn corrosion. Ensure a thorough cleaning before moving on to the following steps.

3. Connect the Multimeter to the Battery

First, affirm that the multimeter is on and functioning, then touch the black negative multimeter probe to the negative terminal, followed by the red positive probe to the positive terminal. If your battery is operating properly, its multimeter output should read about 12.5V. If the voltage is below 12.3V, the battery may just need charging, but if it is below 12.2V, the battery is most likely in need of replacement.

4. Start the Car

Check your multimeter reading with the car running. Ideally, you should have someone else start the car while you monitor the reading. If the voltage drops under 10V, the battery is not providing enough power.

How Often Should You Check the Battery?

To avoid sudden battery failure, you should perform these tests every six months. With that being said, though, there are other signs that can point to your battery being on its last legs.

You may notice that starting the car takes longer than normal: Slow engine starts means the car’s starter motor is getting barely enough power to turn the engine over, and a clicking noise means the battery has died and will not be able to start the car at all. You may also notice that interior lights are unusually dim and that the radio, power windows, power seats, and other accessories are malfunctioning.

By performing a simple battery test, you can stay on top of your car’s health and avoid ending up stranded. Traditional lead-acid batteries should last three to five years, though that lifespan can shorten due to exposure to temperature extremes, heavy vibrations, or a faulty alternator.

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