How Does An EV DC Charging Station Work?

As electric vehicle adoption accelerates, the need for DC fast charging is increasing. Fast DC EV Charging plays a pivotal role in shaping the future of electric mobility by offering rapid and convenient charging solutions for EV drivers.

We have two types of current which are AC and DC. AC stands for Alternating Current while DC is Direct Current. Both of them are two strategies when charging an electric car.

The key parameter when choosing an electric car is the capacity of this on-board (built-in) charger because the car’s charging speed depends on how fast this on-board system can receive the alternating current from the source and also on how many phases it can use.

About AC And DC Charging

Alternating current (AC) is transmitted via power lines, and there are 230V and 50 Hz in a standard electrical outlet in most parts of Europe. Electric current is produced as alternating and it can be transmitted without much loss and over longer distances then it would be the case with the direct current.

Difference Between AC And DC Charging

The key difference is that DC is faster than AC charging. When using direct current, energy can be stored in the battery without being converted, which makes the process more efficient and saves time.

However, to store energy from alternating current, an onboard charger in the EV has to convert it first, which leads to longer charging times.

AC charging

When charging an electric car with alternating current, the car’s on-board system (also called the on-board charger) is used and it takes care of the conversion of outlet current into battery current. It therefore receives alternating current (AC) and converts it into direct current (DC), which is then sent to the car battery.

AC charging station

When charging with AC stations, the electrical grid is connected to the on-board charger. The main function of the AC station is to mediate the necessary communication with the vehicle control system and to ensure the safety of the vehicle and the crew. Moreover, the charger tells the vehicle what maximum current it can draw at that time, depending on how busy the grid is. The AC charging station thus regulates the charging according to the current possibilities of the house or the charging point, so that the network is not overloaded.

AC chargers recommended by Sino
AC chargers recommended by Sino

Advantages of AC charging station:

They are affordable and much cheaper than DC charging stations.

Much more widespread due to their lower price.

significantly smaller and their installation is simple.

Thanks to the above characteristics, they are also suitable for home installation and night charging.

Introduction to DC charging or DC fast charging

DC fast charging, or so-called fast charging, is done using a DC charging station, which can change the alternating current (AC) to direct current (DC), it then “bypasses” the on-board charger of the electric car and sends this direct current via Battery Management System (BMS) to the battery, as instructed by the vehicle’s charging control system.

DC fast charging is a charging method that tops EV batteries up quickly, some in as little as 30 minutes. Unlike AC charging, which is slower and commonly used for overnight charging at home, DC fast charging is designed for short charging stops, making it an ideal option for long road trips.

DC charging station

A DC charging station is technologically much more complex and many times more expensive than an AC charging station and moreover it requires a powerful source. In addition, a DC charging station must be able to communicate with the car instead of the on-board charger in order to be able to adjust the output power parameters according to the condition and capability of the battery.

Mainly due to the price and technological complexity, we can count significantly fewer DC stations than AC stations. Currently, there are hundreds of them and they are located on the main arteries.

How does DC fast charging work?

When charging an electric vehicle with a DC fast charging station, the EV is constantly communicating to control how much power is drawn. Several variables determine the speed at which your EV is charged; however, the main variables we will focus on are the rate of the charging station, the acceptance rate of the electric vehicle, and the DC fast charging curve.

DC Fast charging
DC Fast charging
  1. Rate of Charge of a DC Charging Station

All EV charging stations are measured as their maximum output power in kilowatts (kW), known as the rate of charge or charging rate. DC fast charging stations range from 30 kW to 480 kW; Generally speaking, the higher the kw, the faster the charge, however, choosing a higher kW DC fast charger over a lower kW one does not necessarily mean that the electric vehicle can be charged quicker. This is where the acceptance rate of the electric vehicle influences the charger’s rate of charge.

  1. EV Charge Acceptance Rate

An EV charge acceptance rate is the maximum amount of power in kW that an electric vehicle can input. The vehicle’s battery management system communicates this to the charging station when a Dc fast charger cable is connected to the car. Some early electric vehicles have very low charge acceptance rates, however, more and more EVs on the market have higher charge acceptance rates to improve charging speed.

For example, let’s take a car with an EV charge acceptance rate of 60 kW. That would mean that the rate of charge would be approximately the same regardless of whether it was being charged at a 60 kW, 100 kW DC fast charging station, or even a 350 kW. Let’s look at another example, but the other way around, the Porsche Taycan4 has a charge acceptance rate of 320 kW, meaning it can take a peak charge of 320 kw. it would not reach its peak if you were to charge it at a 150 kW fast charging station. lt would only be able to take in 150 kW as that is the maximum rate of charge of the charging station.

  1. DC Fast Charging Curve

The DC fast charging curve is another influential variable in determining EV charging time. Every EV model has its unique charging curve, which determines how much power it can take over time as it charges.

  1. Is DC fast charging bad for an EV battery?

Not really, The faster the charging, the faster the EV battery capacity will decline, which is technically accurate. Even if the only type of charging used was DC fast charging, the difference in the rate of decline of the EV battery capacity compared to Level 2 AC charging is minimal.

Every electric vehicle battery has an advanced Battery Management System (BMS), which has set parameters specifically configured to prevent damage to the EV battery. The BMS controls the charge acceptance rate and monitors the battery temperature, and if needed, can lower the rate of charge to protect the battery.

While DC fast charging can affect an EVs battery life, it is minimal and doesn’t damage the battery.

Other factors impact the rate of DC charging

  • Temperature

If it’s extremely cold or hot, you may find that charging takes longer than usual because every EV battery has an optimal operating temperature. When temperatures fall outside this range, charging may be slower.

  • State of Charge (SoS)

This is how much charge is left in your EV battery, usually displayed in percentages. A battery that has little energy left will charge faster than a battery that is almost full. DC chargers work fastest between 20% to 80% SoS. Outside this range, DC fast charging rates may be lower.

  • Busyness

A busy charging station, used by multiple EVs at the same time, will charge your car more slowly. The reason for this is how the power supply is set up. DC fast chargers, and any other chargers, are likely connected to the same electricity supply. If demand is higher, every charger connected to the same source will slow down.

How many KW is a DC fast charger?

The higher the output power (kW) of a DC fast charger, the quicker it can potentially charge an electric vehicle. The kW output power can vary depending on the installation location, the brand and the model. Current DC fast chargers on the market range from 30 kW to 480 kW. These can be standalone DC chargers that provide the full kW power to one plugged-in vehicle or split chargers that distribute the power to more than one charging cable, simultaneously charging multiple EVs by sharing the kW power output of the charger.

How many types of DC fast charging connectors are there?

There are currently four types of DC fast charging connectors used worldwide: CombinedCharging System (ccS), CHAdeM0, GB/T, and Tesla Superchargers. Depending on what make and model your electric vehicle will determine which DC connector you can use to charge it. With ccs, there are two types ccs1 which is used in North America, and ccs2, which is used in Europe. CHAdeMO is primarily for Japanese brand vehicles, However, these manufacturers are moving over to the CCS connector for newly released models in North America and Europe. GB/T is the standard connector for the Chinese market, and Tesla’s Supercharger works with all Tesla vehicles worldwide except in the EU.

Different connectors for EV charging station

Advantages of DC charging

  • Rapid Charging: Fast DC Charging enables EV drivers to charge their vehicles significantly faster than traditional AC charging methods.
  • Convenience: With shorter charging times, drivers can spend less time waiting at charging stations, enhancing the overall convenience of electric vehicle ownership.
  • Accessibility: The widespread deployment of DC Fast Charging infrastructure is essential for promoting the adoption of electric vehicles by addressing range anxiety and increasing the accessibility of charging options.
  • Supporting EV Growth: The availability of DC Fast Charging infrastructure is crucial for supporting the growing number of electric vehicles on the road.

DC fast charging is essential for public EV charging infrastructure and will help enable long-distance traveling and give households with no home EV charging somewhere to charge their cars quickly. DCFC will also be critical as we transition larger vehicles to electric, requiring larger batteries and higher charging rates to make them usable in real-world environments. 

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ZHUHAI SINO ENERGY TECHNOLOGY CO., LTD.
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