What Is DC Fast Charging and How Does It Work?
Electric current exists in two forms: alternating (AC) and direct (DC). In alternating current, electrons change direction regularly at a very high frequency, while indirect current flows in the same direction. Alternators in power plants produce alternating current, which is then fed into the public grid. This type of current is used because it is easier to transport and transform while limiting losses. At home, the electricity that reaches our outlets is therefore alternating.
What Is DC Fast Charging
The fast chargers for rechargeable electric vehicles use the DC to load and the conversion of the power takes place before entering into the vehicle. Once the conversion has been completed, the current will flow directly into the battery without passing through the vehicle's converter. However, DC chargers require a lot of current from the network which is around 125 A. Therefore, its cost which includes production, installation, and operation is much higher than expected, which leads to an increase in charging amount or fees for vehicles. However, since this type of terminal can ensure rapid recharging, it is the best way to quickly charge the vehicle's battery for long journeys. These chargers are generally more common on highways than in private homes or business sites.
With the fast-charging station, you can charge your electric car and gain more autonomy in less than two hours. Unlike normal electric charging stations from 3 to 7 kW and accelerated charging less than 22 kW, the powers of these fast-charging stations for electric and hybrid vehicles exceed this value, which makes it possible to recharge 3 times faster and save a lot of time. To make this type of power possible, these charging stations convert the alternating current into a direct current, so that the car can be charged directly without going through a converter, which dramatically reduces recharge time.
Direct current in the battery
When you recharge your electric car at home or on small public AC terminals, the alternating current is transformed by a component embedded under the hood of the vehicle: the converter. This part produces direct current, the only form of electricity that can be stored by the battery (read our file on the operation of an electric car). The direct current then powers the electric motor, which can also generate it during the braking and deceleration phases.
If you need to charge very quickly, it is not essential to opt for an electric car with a high-power converter. You will only have to move to a fast or ultra-fast DC terminal, which itself converts the alternating current into direct current to inject it directly into the battery. These terminals are equipped with a converter and are therefore bulky and very expensive. They cannot currently be installed at a private home. They are most often found in motorway rest areas, certain car parks in supermarkets and car dealerships, and more rarely in public car parks. This type of charging is ideal for garages and for those who travel frequently, as well as for individuals who drive long distances and therefore require a large vehicle load. The charging time depends on the energy capacity of the battery and also on the power of the fast charger.
Theoretical maximum power in DC
If all-electric cars currently on the market can now recharge with direct current, they do not accept the same power. The Renault ZOE 52 kWh is for example limited to 50 kW while the Hyundai Kona and Kia e-Niro accept up to 77 kW. The Peugeot e-208 can charge up to 100 kW and the Tesla Model 3 up to 250 kW. Porsche even plans a charging capacity of up to 350 kW for its Taycan in 2021. However, these powers are not guaranteed and correspond to the maximum peak that the vehicle can reach during a charging session. This does not mean that the car will charge throughout at this intensity: this is a theoretical indication to get an idea of the DC charging capacity.
The exact charging time depends on the vehicle and the temperature of the battery (if too high). The terminals of fast charging are usually located on highways and major urban areas. Consequently, several electrical networks are developing to increase the possibility of recharging electric and hybrid vehicles or recharging infrastructures.
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