Is a car battery AC or DC?

Alternating Current (AC) and Direct Current (DC) are the two methods of transporting power from one place to another. From a battery to the starter motor on your car or from the power station to your home, AC and DC are what make it happen. 

But what are the differences, and which type of current does your car use? We briefly look at the differences and explain the system used on your car. 

Alternating Current vs. Direct Current 

As the name suggests, alternating current is not a steady flow but switches from positive to negative. This output produces a sine wave with peaks equal to the voltage, as shown below.  

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The rate at which the current switches direction is measured in Hertz, where 50 hertz means the current changes direction 50 times per second. The two halves of the sine wave are called the positive and negative phases. The speed of the alternating current is called the frequency. In the USA, the standard frequency of AC is 60 Hz, while in many other countries it is 50 Hz. 

AC is produced by power stations and used for most households and businesses to power their equipment. The symbol for AC power is usually a sine wave in a circle; 

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Direct current, on the other hand, has a constant voltage and direction of current flow. DC is used to power the electrical devices around your home, such as mobile phones and your television. Any electrical item that uses an AC adaptor or charges via USB uses DC power. We also use DC power to charge batteries. If you see the symbol below, the device is DC-powered. 


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Is A Car Battery AC Or DC? 

All batteries provide DC power. This is because batteries have fixed terminals, and the current flows from positive to negative in a constant flow. It is possible to convert the DC output of a battery into AC using an inverter if required. Your car battery is charged by the car’s alternator, which produces AC, but is passed through a rectifier that converts it to DC before it reaches the battery. 

What are the advantages of DC over AC? 

AC and DC power are used for different purposes. AC is used in power generation because it is far more efficient to transmit high voltage AC over long distances. But if that’s the case, why not use AC power for your car battery? The efficiency advantage reduces at lower voltages, but more importantly, DC provides a constant voltage and current. 

Why can we not store AC like DC? 

In AC power, the positive and negative outputs swap at the speed of the power source that is generating the current. The switching rate is measured in Hertz, and in the USA, it is set at 60 Hz. Because a battery works using chemicals, not a rotating generator, it isn’t possible to switch the fixed terminals.  

The other issue is charging a battery with AC, which is not possible. As the AC switches phase, the positive phase will charge the battery, but the negative phase will discharge the battery.  

Are Other Batteries AC Or DC? 

Have you ever wondered if any batteries are AC and not DC? Well, no need to wonder anymore! All batteries are DC. It doesn’t matter if it’s on your motorcycle, powering your television remote control, or under the hood of your car. They are all DC-powered. 

As we discussed earlier, it just isn’t possible to store AC power in batteries. 

Is The Current In Your House AC Or DC? 

The main power supply to all buildings is AC. This is universal worldwide because of the advantages of AC for electrical power transmission over long distances. 

Because the AC is switching at 50 or 60 hertz, anything powered directly by AC will be flickering, but our eyes don’t notice it. Interestingly, babies do see the flickering as their eyesight hasn’t fully developed. This is why you’ll often see babies staring at lights, as the flickering attracts their attention. 

Since an AC supply powers your house, how do your DC electronic items work? Anything that needs a DC supply in your home will be supplied with an AC adaptor, or a built-in adaptor will produce the DC required. 

So Which Is Safer: AC Or DC? 

In reality, both are dangerous but at different voltage and current levels. It is always essential to treat any electrical supply with caution.  

The first thing to understand is that the current and not the voltage causes an electric shock. The voltage is the electrical potential, and the current is the flow of electrons through resistance or load. The human body offers a resistance to the flow of electrons at varying levels, and therefore the current flow will vary. 

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The relationship between voltage, current, and resistance is defined by the equation; 

I = V divided by R (Ohms Law) 

Where I = current, V = voltage and R = resistance. 

The equation means that as the resistance decreases, the current will increase for a set voltage level. The human body has different resistance levels in different areas, but the resistance at the contact point reduces the longer it is in contact. Resistance also reduces with humidity, making better contact between your body and the conductor. 

AC vs. DC voltage 

AC voltage has two peaks, the positive and negative values. When an AC voltage is quoted as 220 volts, the peak voltage is higher, whereas an equivalent DC voltage of 220 volts is constant. This means that 220 volts AC will pass a larger current than the identical DC voltage through your body, making it more dangerous. 

AC frequency 

AC is also more dangerous because it changes the current direction at a rate of 50 or 60 hertz. This frequency interferes with the body’s muscles and nervous system and can prevent the victim from letting go of the conductor. 

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