Are Cars AC or DC?

It’s quite fascinating to imagine all of the many different processes at work when you drive your vehicle. 

Besides fuel, electricity is the most important factor when it comes to powering most vehicles. Most people already know this, but probably take for granted how the whole process works.

You might understand the basic principles of AC and DC current, but which of these two currents power your car?

Car batteries produce DC current, which powers most of the vehicle’s processes. However, your vehicle requires a steady flow of AC current from the alternator to replenish the battery’s charge. Without both AC and DC current, your vehicle won’t run for long.

How Do Car Batteries Work?

You have to understand that your car has a battery that produces and distributes DC current across all the vehicle’s electrical components. 

It also has an alternator that generates AC currents that convert it into DC current and stores it in the battery for future use. 

Therefore, a car has both currents but uses DC current.

History Of Car Batteries 

A long time ago, internal combustion gasoline cars had magnets that acted like crude alternators. 

They served simple electrical systems in cars without batteries. This technology was the idea of Hippolyte Pixii.

The alternator was useless until solid-state electronic technology came in the late 1950s. 

This technology used silicon diode rectifiers to convert AC current to DC current which could be used in cars.

The leader in the use of alternators in vehicles during this period was Chrysler. 

They were already exposed to the use of electronic voltage regulators and rectifiers because of their research work sponsored by the Department of Defense.

The first vehicle in the market with a standard alternator was the 1960 Plymouth Valiant.

The more noticeable difference from other vehicles thanks to the alternator was at low speeds, there was still enough current produced to charge the battery

This wasn’t possible with DC generators.

In addition, the alternators were cheaper to produce, lasted longer than DC generators. 

This was a game-changer for the vehicles produced since then thanks to the reliable, cheap, solid-state rectifier. 

Read on to learn how a car’s electrical system works. 

AC & DC Current Explained

Direct Current (DC) is a type of electricity batteries produce and flows in one direction. 

A generator also produces DC current, which most vehicles from 1900-1960 used. 

Thomas Edison used DC current in the first electric gadgets he invented.

Alternating Current (DC) changes direction periodically and it is typically in sockets and other wall outlets.

Nicola Tesla used AC to power his inventions. 

It is preferred for homes, buildings, and cities because it is easy to transmit AC current over long distances, maintaining the same power.

Most electronic gadgets used at home including cars, use DC internally. 

Therefore, it has to convert the AC current from the outlet into DC. 

The plugs connecting the electronic device to the outlet have hardware that helps with this conversion as well as keeping the heat produced in the process low.

There are no AC batteries, therefore, you can use an AC converter with a DC battery. 

This allows you to have more control over the energy produced by the battery but with the ability to store this power in a portable unit. 

An example of this is the power grid that supplies power into your home.

Do Cars Run On AC or DC?

In a car, the battery supplies DC current across the vehicle but the alternator generated AC. 

So, the question here is, how does the car battery function?

Most cars use a sealed lead acid battery but there are newer car models that use lithium-ion batteries. 

The lead-acid battery has 6 cells that produce 12.6 Volts although their capacity will differ based on the size and power needs of the vehicle. 

For example, a small car will use a 65 – 80AHr range in batteries while SUVs will use 100 – 120AHr batteries.

Are Car Batteries AC or DC?

Electricity is the flow of electrons from the positive end to a negative end in a circuit. 

Everything in existence has an electric charge but, in most cases, it’s too small to detect. 

They made batteries to power motors that use chemical processes to produce electricity.

Most of the components in a vehicle will run using DC currents. 

Therefore, the car’s battery will use a DC current to power these electronic components. 

However, the battery cannot store energy indefinitely and will eventually discharge completely and all the components will shut down.

This is the reason why vehicles have alternators, a small generator, which will convert mechanical energy during car movement into electrical energy. 

This will in turn be converted into chemical energy which is the only way you can store energy

Whenever an argument arises whether car batteries are AC or DC, it’s important to remember that electrical appliances and low voltage power systems will use DC current.

Do Car Alternators Produce AC or DC Current?

To maintain the charge in a battery, an alternator will have to continuously produce a three-phase AC current. 

This AC current from the alternator is converted to DC current immediately.

Originally, vehicles used DC generators (dynamos) instead of alternators for power. 

With time the vehicles had more complicated designs with more electronic components. This increased the average power consumption which the DC generators couldn’t sustain.

The alternator replaced the DC generators because of their efficiency in charging a variety of RPMs.

Compared to the DC generators, alternators increased excitation in their field windings so as to produce more power at a low RPM.

The alternator produces AC current, which can’t be used in electronics. 

Therefore, it has to be converted into DC current which is done using the 4 diodes of a full-bridge rectifier. 

The DC current goes into the battery and the battery stores it as chemical energy for future use. 

Bottom Line

For a layman, a vehicle’s electrical system might be hard to understand. 

Despite the complexity, the electrical system is the heart and soul of the vehicle. If it is faulty, the vehicle will not run at all. 

In summary, all you need to know is that the car battery is DC and should be inspected and cleaned on a regular basis. 

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Hi, I'm the founder of VehicleAnswers.com! Having owned a wide variety of vehicles in my life, I was astounded at how hard it can be to find answers to common automotive questions. Rather than sit idly, I decided to create this website to help others!