Are Car Batteries AC or DC? [Explained]

There are two types of batteries in a car. One is the system backup battery and the other is the battery that runs the car. The 2nd one is used in hybrid or electric cars. We all know there are two types of batteries. But do you know what types of batteries are used in a car? Are car batteries AC or DC?

Car batteries use DC current because AC power can’t be stored in batteries. Since AC or ‘Alternating Current’ switches back and forth, it’s a little more complicated to use in car batteries.

Scroll down to know the details about whether a car battery is DC or AC, the working process of both AC and DC batteries and let’s find out what other factors make a DC battery more suitable for cars.

Basics of AC and DC Batteries

Before we get into whether a car battery DC or AC, let’s check the basics first. Simply put, AC refers to the Alternating Current. It’s nothing but the streaming of electrons. But the direction those electrons follow differs from AC to DC current.

While AC current alternates the direction throughout the journey, DC imoves in a straight line from the reservoir to the engine of your vehicle. AC current was first invented by Nicola Tesla and DC was invented by Thoms Edison.

For alternating the direction, AC current creates a curve wavelength. It provides long-distance travel of electrons without power loss. By diverting the line, the AC current adjusts the voltage so it doesn’t harm any appliances. 

On the contrary, DC delivers voltage in a more consistent way. A battery is the main source of DC current but you can convert AC to DC by using a rectifier as well. Note that, batteries can not store AC power.

Are Car Batteries AC Or DC?

So, is a car battery AC or DC? As we stated before, batteries cannot store AC power. So, of course, car batteries are DC.

The main reason why a car battery doesn’t run on AC power is the frequent changes of direction in AC power. I mean, imagine AC power changing its direction 50 times per second. It will require the battery to change its every terminal’s polarity at the same interval (I mean, yes, 50 times in a second) which is close to impossible.

Moreover, imagine you’re storing AC power in a battery. To do so, you have to connect an AC supply to a battery which means it’s only possible to charge the battery during the positive half cycle.

Similarly, the battery can discharge the power during the negative half cycle. If you count the average voltage or current in a complete cycle, you’ll get zero. Therefore, the chance of storing AC power in a battery is a big zero.

Also, the fact is, DC power also cannot be directly stored in a battery. However, it’s stored in the battery for future use only after getting converted into chemical energy.

Although there are no AC batteries, AC current can be generated by converters. If you use an AC converter on a DC battery, it will offer more control of the energy source and keep the power in a portable battery unit.

The power grid is one of the most common examples where DC batteries are associated with AC converters. And, the electronics of your car mainly use DC power because it flows in a single direction which makes it easier to control the transistors of the electronics.

Why Is A DC Battery Used In A Car?

The biggest compelling reason for it is that DC batteries offer high efficiency at a lower cost. It helps transfer more power over very long distances (more than 1,000km) ensuring low electrical losses.

Also, it reduces carbon emissions so there’s less impact on environmental disasters.

While AC chargers need another converter, DC chargers have a converter inside the charger itself. So, a DC charger doesn’t need an onboard charger to convert it. Instead, it can feed power directly to the battery of your car.

Overall, DC chargers are a more suitable, faster, and bigger option for a car battery compared to an AC.

Differences Between AC And DC Battery

You already know whether a is car battery ac or dc. There are so many differences between these two types of batteries. Among them, most differences are told in the definition of both battery types. Let’s learn some more differences between them.

Differentiating FactorsAC BatteryDC Battery
What does it use to operate?AC battery uses alternators to workDC battery does not use alternators and works on direct current
Charging TimeFaster ChargingSlower
Light Supplying CapabilityBetterGood
PriceMore expensive when used in carsLess expensive
Risk FactorsIt’s more dangerous working with AC than with DCIt’s easier and less dangerous working with DC

So, these are the most common dissimilarities between AC and DC batteries.

Some other differences are also there like AC power tends to heat and spark more which can cause electric shocks and even fire. It happens because an AC generator produces higher currents compared to a DC generator.

Although AC power systems have always been a great option, the times when you can’t use AC current over very long distances, a DC car battery always gets your back covered.

And, the reason why we’ve stated that AC is more expensive when used in cars is that you need to convert AC to DC during charging or for storing the power in your car’s battery. For this, you need to pay an additional amount.

So, overall, these are the reasons why a DC battery is different from an AC battery and why the first option is always better for vehicles.

Is An Alternator AC or DC?

Well, the alternator of your car is AC; it creates a three-phase AC current. However, the AC current that’s generated by the alternator is immediately converted into DC.

Alternators are highly efficient when it comes to charging a wide variety of RPMs. For this, alternators are a newer and much more needed addition than DC generations. Unlike DC generators, alternators increase excitation in their field windings and offer higher output at low RPM.

Still, since the alternator provides AC output (which isn’t used in electronics), the AC power of the alternator needs conversion into usable DC. It’s possible because of the previously-mentioned equipment ‘rectifier’.

There are four diodes in a full-bridge rectifier that converts AC power into DC. After the electrical power is turned into DC, it reaches the storage of your car’s battery.

Yes, this is a brief of car mechanisms.


Hopefully, you’ve got your answer to this question- ‘are car batteries DC or AC?’

The battery is a vital part of a car. So, while changing it, be careful about its type. We hope now you know what types of battery is used in a car. There are some more discussions on our site about cars. You may read them too for a better understanding of cars’ problems and their solutions. Thanks for reading from us.

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William Baldwin

This Is William Baldwin, The Founder & Managing Editor of this website. Me and my team share automotive tips, tricks, and news

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Talha Atta

Talha Atta, a Mechanical Engineer and experienced technical content writer and editor at with a passion for the automotive industry.