AC vs. DC Charging: What are the Differences?

Electricity is the backbone of all electric vehicles.

With competitive price and timely delivery, Ruihua sincerely hope to be your supplier and partner.

However, not all electricity is of the same quality.

There are two main types of electrical current: AC (alternating current) and DC (direct current).

In this blog post, we will explore the differences between AC and DC charging and how they impact the charging process of electric vehicles.

But before we delve into the details, let's clarify something first.

Alternating current is what comes from the power grid (i.e., your household outlet).

Direct current is the energy stored in your electric car battery.

EV charging: the difference between AC and DC

AC vs. DC power

DC power

DC (direct current) power is a type of electrical power that flows in one direction.

Unlike AC power, which changes direction from time to time, DC power flows in a constant direction.

It's often used in devices that require a constant, steady power source, such as computers, televisions, and smartphones.

DC power is generated by devices such as EV batteries and solar panels, which produce a constant flow of electrical current.

Unlike AC power, which can be easily transformed to different voltages using transformers, DC power requires a more complex conversion process to change its voltage.

AC power

AC (alternating current) power is a type of electrical power that changes direction every now and then.

The direction of AC voltage and current changes periodically, typically at a frequency of 50 or 60 Hz.

The direction of the electric current and voltage reverses at regular intervals, which is why it's called alternating current.

The AC electricity flows through the power lines and into your home, where it is accessible through the power outlets.

AC and DC charging pros and cons

AC charging pros:

1. Accessibility. AC charging is accessible to most people because it can be done using a standard electrical outlet.
   This means that EV drivers can charge at home, work, or public places without specialized equipment or infrastructure.

2. Safety. AC charging is generally considered safer than other charging methods because it delivers power in a sine waveform, which is less likely to cause electrical shock than other waveforms.

3. Affordability. AC charging is less expensive than other charging methods because it does not require specialized equipment or infrastructure.
   This makes it a more cost-effective option for most people.

AC charging cons:

1. Slow charging times. AC chargers have limited charging power and are slower than DC stations, which can be a disadvantage for EVs that require fast charging on the road, such as those used for long-distance travel.
   Charging times for AC charging can range from a few hours up to days, depending on the battery's capacity.

2. Energy efficiency. AC chargers are not as energy-efficient as ultra-fast charging stations because they require a transformer to convert the voltage.
   This conversion process results in some energy loss, which can be a disadvantage for those who are concerned about energy efficiency.

DC charging pros:

1. Fast charging. DC charging is the fastest charging method available for electric vehicles (EVs). It can charge an EV in as little as 20-30 minutes, depending on the capacity of the battery being charged.

DC charging cons:

1. Accessibility. In certain regions, rapid charging stations may be scarce or widely dispersed. Not all public charging stations have fast charging equipment, so EV drivers will have to use an app to locate nearby DC chargers.

2. Cost. Charging at DC charging stations can be costly, depending on location.
   Some are free for the first 30 minutes, while some charge a fixed fee.
   The bottom line is, it's more expensive than AC charging.

3. Battery degradation. Frequent fast charging is known to have adverse effects on a car's battery.
   The charging curve exhibits degradation, wherein the charging process initiates at a rapid pace, but gradually decelerates as the battery approaches its maximum capacity.
   In comparison, AC power travels in a flat line since the onboard charger can only accept limited power spread over longer periods.

What is the difference between AC and DC EV chargers?

Differences between AC and DC chargers

AC chargers for EVs are similar to AC chargers for other devices.

An AC charger uses a sine waveform to deliver power to the electric vehicle battery.

The voltage used for an AC charging station is typically between 110-240V, depending on the country and electrical standards.

This is relatively slow compared to a DC charger, with charging times ranging from a few hours to days, depending on the battery's capacity.

Because of this, AC charging is also known as slow or trickle charging.

AC chargers deliver power to the EV's onboard charger, which then converts AC power to DC power that can be used by the EV battery.

AC chargers are typically used for home charging and can often be plugged directly into a regular household outlet.

Meanwhile, DC charging stations are significantly faster and more efficient than AC chargers.

DC fast charging uses a constant waveform to deliver power to the electric vehicle's battery.

Unlike an AC charger that needs an on-board charger to convert AC power, a DC charging station already has a converter inside, which allows it to deliver energy directly to the car batteries, effectively increasing the charging speed.

The voltage used for DC fast chargers is typically between 400-800V, which is significantly higher than the voltage used for AC charging.

This higher voltage allows for faster charging times, with some EVs being able to charge in as little as 20-30 minutes.

Because of the significant amount of power required, DC chargers can only be found in commercial EV charging stations.

AC vs. DC Charging: adopting the most practical solution

Mixing AC and DC charging

Mixing AC and DC charging for electric cars can be a practical solution for some EV owners.

This is because AC charging is more widely available and less expensive than DC charging, while the latter provides faster charging times.

One way to mix AC and DC charging is to use AC charging for daily charging needs and DC charging for long-distance travel or when fast charging is required.

This allows EV owners to take advantage of the convenience and accessibility of AC charging for daily charging needs, while still having the option to use DC charging for fast charging when necessary.

Another way to mix AC and DC charging is to use a hybrid charger that combines AC and DC charging capabilities.

These hybrid chargers can provide both AC and DC charging from the same charging station, which can be a practical solution for EV owners who want the flexibility to use both types of charging.

However, it's important to note that not all EVs are compatible with both AC and DC charging.

If you want to learn more, please visit our website Ac and Dc Charger.

Some EVs require specialized charging equipment, which may not be compatible with all charging stations.

In addition, mixing AC and DC charging can be more expensive than using AC charging alone.

DC charging is more expensive than AC charging and may require additional fees or subscriptions to use.

FAQs

How does a vehicle battery work?‍

Electric vehicles use lithium-ion batteries to operate. Lithium ions are released from the positive electrode when the battery is charged and move through the electrolyte solution to the negative electrode, creating a potential difference that produces electrical energy. When the battery is discharged, the process is reversed, and the lithium ions move back to the positive electrode, releasing electrical energy to power the vehicle.

Is AC or DC better for charging?

This will depend on your charging needs. If you drive short distances on a daily basis, then regular top-ups using an AC charger should be enough. But if you're always on the road and are driving long distances, DC charging is the better option, as you can fully charge your EV in less than an hour. Do note that frequent rapid charging could cause battery degradation as the high power produces too much heat.

Does DC charge faster than AC?

Yes, DC charging is faster than AC. DC chargers can deliver power directly to the car's battery without relying on the EV's onboard charger. This eliminates the need for conversion and speeds up the charging process. AC chargers provide between 3-40 miles of range per hour of charging, while DC fast chargers can charge batteries from 0 to 80% in just 20 minutes.

Is Tesla AC or DC charging?

Tesla uses both AC and DC charging. The Mobile and Wall Connectors use alternating current, while the Supercharger uses direct current.

Is AC charging better for batteries?

In the long run, AC charging is better for battery health as it doesn't put too much strain on the battery. Since DC charging requires more power, it produces heat that degrades the battery faster.

Do EVs run on AC or DC?

Electric vehicles run on direct current. The battery in an EV stores electrical energy in a DC format, and the electric motor that powers the vehicle runs on DC power as well.

For your EV charging needs, check out Lectron's collection of EV chargers, adapters, and more for Tesla and J1772 EVs.

For many people, it doesn’t matter. DC is faster, and that is all that they need to know. But for the curious, this is a simplified explanation of the difference between AC and DC charging. Technical details are intentionally glossed over here.

The reason we have two types of charging is that there are two “types” of electricity, AC and DC; so we shall start by discussing them.

AC VERSUS DC

DC is the simple positive-and-negative type of electricity that you probably experimented with in 7th grade science. A key advantage is that it is easy to store in batteries. That is why portable electronics – flashlights, cell phones, laptops – use DC power; they have to store it. Plug-in vehicles are portable so they use DC batteries too (although most of them have AC motors – a complicating step we may consider another day).

AC electricity is a little more complicated because it switches back and forth, but a key advantage is that it can be transmitted economically over long distances. That is why AC power comes in through the power lines to your home, and is what is available at power outlets. Stationary appliances that use electricity directly from an outlet – lamps, refrigerators, washing machines – use AC power.

Because the electric grid provides AC, the electricity must get converted to DC when you want to charge a portable device. This conversion is done by a “rectifier”. Portable electronics that recharge from wall power all have one: it is usually in a black box in the charging cord, along with some other components we will ignore. You’ll notice that the more power the device uses, the larger that box is. The key to understanding AC versus DC charging is learning where the box is, and why.

CONVERSION IN PICTURES

Here is the DC charging solution for my tablet computer. It is simply a USB cable, which allows my tablet to charge from a DC USB port in a car or laptop. Both sides have DC, so no conversion is required.

Now, here is my tablet’s AC charging solution. The same USB cable plugs in to a little black box that plugs in to an AC outlet – the box converts AC to DC.

Here is a simplified diagram (can you tell I didn’t take art classes?) of how AC and DC charging work with a plug-in vehicle:

When you plug in to AC power – whether you plug in to a 120V or 240V outlet, or use J1772 charging equipment – your car converts the power to DC.

When you use a DC charging station – CHAdeMO and Supercharger are the varieties in active use, with CCS coming soon – the power is converted by the station, so DC goes straight in to your battery (not really, but close enough for this discussion).

Note that in both cases the power starts as AC and ends up as DC; the only qualitative difference between “AC charging” and “DC charging” is whether the conversion is done before or after it goes in to your car.

WHY USE BOTH TYPES?

Why bother with two types of charging – why not choose a single place to convert the power?

AC is more readily available at power outlets, but despite AC lines carrying vast amounts of power, outlets are limited. Dedicated DC charging stations provide more power, but being expensive to install and dedicated to plug-in charging, availability is limited.

AC PROS AND CONS

AC outlets are ubiquitous, so to make charging convenient your car should be able to plug in to them. That means every car has to be able to convert AC to DC. The conversion equipment in current plug-in cars varies; most can convert up to 3.3, 6.6 or 9.6kW of power.

For comparison a typical household outlet can continuously provide up to 1.4kW, and “high-power” 240V outlets sometimes found in garages and RV parks can provide up to 9.6kW. It is technically possible for a car to convert far more power than that, but the equipment would be bulky, heavy, expensive, and hot – and anything over 9.6kW would see infrequent use because higher-power outlets are not available.

To illustrate this point: the Tesla Model S offers a $1,500 option that allows the car to convert up to 19.2kW. Twice-as-fast charging is obviously an enormous benefit when you can use it, so some owners swear by it – but you can only get that much power if you use special hard-wired 240V charging equipment. The West Coast has a few such chargers along popular travel routes, but such equipment is hard to find, not needed for overnight charging, and still far slower than DC charging. Many owners skip this option to save money and weight.

DC PROS AND CONS

DC charging stations have special grid hookups so they can get and convert far more power. DC stations are big, expensive and have a lot of cooling – it wouldn’t be practical to put that equipment in every car, even if there was a way to plug directly in to the grid.

CHAdeMO chargers vary from 25 to 60kW, and Superchargers are 90 to 120kW – almost 100 times faster than a standard 120V household outlet, and more than 10 times faster than 240V AC outlets.

At higher cost, the grid could supply even more power; but these limits are largely set to avoid harming the car batteries while charging. (Many factors determine how fast batteries can charge, but currently cars that use Superchargers have significantly larger batteries than cars that use CHAdeMO chargers. All else being equal, larger batteries can accept more power without harm).

EXAMPLE: MODULAR CHARGING

An easy way to visualize the AC/DC charging differences is to consider how Tesla handles charging for their Model S sedan. They make large quantities of boxes they call “chargers” that include a 10kW rectifier to convert AC to DC. Every car they build gets one for AC charging, and so can handle all the power than any outlet provides. Plugged in to the right outlet, this can charge a car at up to 24 mile of range per hour.

If you buy “twin chargers”, you get two boxes in the car and can now handle high-power hard-wired charging equipment as well. This can charge the car at up to 50 miles of range per hour.

Tesla’s DC Superchargers have a stack of 12 boxes installed at the station so the car doesn’t have to do the conversion. This can charge the car at up to 300 miles of range per hour.

The boxes that do the power conversion are essentially the same; AC versus DC is largely a matter of whether the boxes are in the car or in the charging station, and how many of them there are.

FEEDBACK

Did this help you understand the difference between AC and DC charging, and why both types are important? Did you see any mistakes? (Not counting omitted details as they were left out on purpose to keep it simple – unless they are salient). Do you have additional or different points to help understand the difference? Are there related topics that you would like to know more about? Please let us know.

Posted by Chad

Images courtesy Plug In America, Aerovironment, Schneider, Microsoft Office Clipart

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