How to test a car battery with a multimeter

How to test car battery with a multimeter

A multimeter is a useful tool to measure electrical currents, including batteries. While you’re probably not going to use a multimeter to measure the AA batteries in your TV remote, you should measure the battery of your car often. Over time, a car battery can run out of juice, and you don’t want to be caught with a dead battery. Here are some frequently asked questions to help you out.

When to test your car battery?

In order to answer this question, we should first tell you how long a car battery lasts on average. For US drivers, you can expect around 4-5 years of battery life, usually 4.5. Some types of battery could last longer, and you should always check the average time your car battery should last.

Because of this, a good rule is to test your car battery near the halfway point, so two years.

Of course, there are other factors that can prolong or reduce your car battery life. For example, if you live in an area where it’s colder or warmer than usual, the weather extremes can be taxing on your car battery. Doing it twice a year, especially before an extreme season, may be needed.

When it’s hot outside, the battery acid can evaporate and the battery in general may start to corrode. Meanwhile, the cold weather may make it harder to start your car, and if it gets frozen entirely, you may have to replace the battery. In this case, you may need to keep your car as warm as possible.

Why did your battery die?

If your car battery is dead, there are many culprits. Let’s look at some of the most common reasons why your car battery could be dead.

It’s Old

Let’s begin with the most obvious reason. If you’ve had your car battery for years, it may be worn out and ready to be replaced.

You Left Your Lights On

This is a problem that is becoming less and less of an issue due to automatic headlights and interior lights that will shut off after time, but it still can happen. Even if you have automatic headlights, perhaps you accidentally switched them to manual and didn’t realize it. Without the engine running, the lights will kill the battery.

This is known as parasitic drain, and it can also happen due to bad wiring or other interior issues.

Temperature Extremes

If you leave your car in extreme temperatures on either side, it can have a negative effect on your battery. Try to keep your car in shelter when you’re not using it.

Defective Charging System

This can happen when your alternator belts loosen, or the tensioners wear out. This can prevent your battery from charging all the way, even when you’re driving it.

You Don’t Drive it For Long

If most of your drives are short, then it can run down your battery faster. This is because you don’t have enough time to recharge the alternator of the car. We aren’t saying that you need to walk everywhere that’s under a 30 minute drive, but if the place you’re going to is only a couple blocks away, consider it.

Cables Have Been Corroded

This can happen due to extreme weather, or with time. Another thing to consider is if the cables are too loose.

How to test your battery (safely) with a Mutimeter?

Here is how you can get the most out of your multimeter when you decide to test it.

  1. While keeping the car off, turn the headlights on for a couple minutes. This can eliminate surface charge, which can give you readings that are inaccurate. This is something you should do with most batteries, as it can give you false readings.
  2. Before you turn the headlights off, make sure the multimeter is set at 15-20 volts.
  3. Then, connect the multimeter. Make sure the positive and negative terminals are connected well.
  4. Look at the voltage. If it’s not in the 12.6 volt range, this could be a sign your battery is bad.
  5. Start up the car. You should see the voltage change to over 10. While the car is running, pay attention to the levels. If it goes under 5, you should get a new battery ASAP.

 

Can you test different sized batteries with a Multimeter?

Yes, you can, but only batteries that don’t need any maintenance. These are batteries that don’t have any plastic caps on their cells. If you do have a maintenance battery, use a hydrometer to test it instead.

Conclusion

Your car battery is important, no matter how new or old your car is. Check your car battery regularly in order to make sure it’s running good, and replace it if you suspect it’s bad.

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