AC vs. DC Charging: What are the Differences?
Electricity is the backbone of all electric vehicles.
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:
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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. -
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.
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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:
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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. -
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:
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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:
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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.
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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. -
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.
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.