How To Test Your Car Battery

There’s not much out there that can frustrate like your car battery being dead when you need to head out to work in the morning. This is why it’s important, as a vehicle owner, to know how to test your car battery and to look out for the signs of when to replace a car battery.

Reasons your car battery could be dead

There are several key reasons that your car battery could be dead. We’ve created a list of these reasons for you below:

Accidentally leaving something on

We’ve all done it, left the lights on when you’ve parked, and got back to a car that won’t start. Another big culprit is turning on the interior light and forgetting to turn it off when you get out of the car. Alternatively, you leave the door open and the interior light stays on, draining the battery. Doing this once in a while won’t damage your battery too much, but it will mean that you’ll need a jump start to get going. Just don’t make it a habit or you will need to replace your battery sooner rather than later.

Problematic parasitic draw

There are plenty of accessories in a car that draws power from the battery even when the vehicle is turned off. These include your car clock, the alarm, and the remote sensor for locking or unlocking the doors. This is called a parasitic draw and is completely normal. However, there are times when one or more of these accessories malfunction or there is an electrical short in the car, and too much power is drawn from the battery.

Age and corrosion

It could simply be that your car battery is old and just needs to be replaced. Corrosion caused by old age or leaks from the battery will also lead to problems with the battery keeping a charge when not in use.

How to test your car battery

Now that you know what signs to look for to see if your battery is at fault, it’s important to test your car battery. There are some easy tests that you can do at home that will show you when to replace your car battery.

Test your car battery without tools

There are some ways you can check out what is going on with your battery without any fancy equipment or even needing to leave your driveway. Your first step should be to physically inspect your battery on a regular basis. If there are any signs of corrosion, especially on the terminals, this could mean that your car battery needs to be replaced. If you catch it early enough, you can clean the corrosion off with baking soda and an old toothbrush. This will give your battery some extra lifespan.

You can also test your battery by seeing if it can handle an extra load when starting your car. Turn on your headlights while your car is off, wait 10 minutes, and then try starting your car. If your car struggles to start or the headlights dim significantly during the starting process, it means that your battery is weak and quite probably in need of replacing.

Test your car battery with a multimeter

A digital multimeter is a useful tool that will show you immediately how much charge is in your car battery. They are also called digital voltmeters, digital volt-ohm meters, or simply digital meters, and are readily available online.

Start by setting the voltage on your meter to DC. Then attach the negative wire to the negative terminal on your battery (both will be black) and the positive wire to the positive terminal (both will be red). On a healthy battery, you should get a reading of 12.6V. Anything under 12V means that your battery is low and in need of charging.

Test your car battery with a hydrometer

A hydrometer is similar to a multimeter but needs to have the needle on the front placed into each cell of the battery, one after the other. Start by carefully removing the cap off the cells, and then put the needle straight down into the first cell. Squeeze the hydrometer gently and release so that the needle can draw up some of the electrolytes from the cell. After making a note of the readings from each cell, you can compare your information with the stats from your car’s handbook.

Is my car battery dead?

Aside from these tests, there are also some tell-tale signs that you can look out for that could mean that your battery is in need of replacing:

The engine light

Most modern cars have a built-in warning system that will tell you if your battery is getting old and can no longer do its job. It’s vitally important that you keep an eye on your engine warning light and understand what it means when it and other warning lights come on. That could mean the difference between a minor inconvenience of replacing your battery before anything bad happens or breaking down on the side of the road and needing to get several elements in your car fixed or repaired.

Car not starting easily

As a battery gets older, it becomes harder for your car to start. You’ll notice that it takes a few tries with the ignition key to get the motor to turn over, and you may have to pump the accelerator pedal a few times. This isn’t always a symptom of an old or dying battery though, so it’s a good idea to then test the battery if you aren’t sure and think it could also be the starter motor.

Bad smell coming from the battery

When a car battery springs a leak or gets a puncture, the smell can be quite strong. In these cases, you’ll notice a smell like rotten eggs coming from under the bonnet. It’s essential to get your battery replaced in this case because the leaking sulfuric acid could easily damage other parts of your car.

Misshapen battery

Sometimes extreme or rapid changes in temperature can cause a battery’s outer casing to become swollen, lumpy or much bigger than it’s supposed to be. This is caused by a chemical reaction happening inside due to the temperature fluctuations. Again, it’s essential to get rid of a battery in that condition as quickly as possible because it is now in a weakened state that could end up damaging your car.


How To Test Your Car Battery
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How To Test Your Car Battery
There’s not much out there that can frustrate like your car battery being dead when you need to head out to work in the morning. This is why it’s important, as a vehicle owner, to know how to test your car battery and to look out for the signs of when to replace a car battery.
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Zena Racing
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