AC / DC Charging
Electric current in EV world
What is alternating and what is direct current. What is difference between AC charging station and DC charging station. How fast could EV car be charged and what in fact we need to charge our car? What are the key parameters when choosing an EV?
Electric current comes in two forms:
- Alternating (AC)
- Direct (DC)
The distribution network in Europe transmits in the vast majority of cases alternating current and in a standard socket, there is 220 - 240 V alternating at 50 Hz frequency.
Most of modern electronics is based on integrated circuits and batteries, which require for their operation direct current, therefore, you can charge or operate them only with a power source, which transforms alternating current (AC) from a standart house socket into a direct current (DC). Typical example of such device is a mobile phone charger or laptop. The same direct current is used by electronics and batteries of an electric car.
While using alternating current for charging, a so called "onboard" charger, which is integrated in most electric cars is utilized. It takes incomming AC and transforms it into DC, which is then being sent into the battery pack. The key parameter, when you choose electric car, should definitelly be the power of on-board (integrated) charger, which defines and limits how fast, it can be charged on much cheaper and much more widespread AC charging stations.
Normally, we have three types of sockets providing alternating current (AC) power:
* depending on your country and distributor of electric energy
1phase plug (schuko) .... 3,7kW
3phase plug (16 A) ........ 11kW
3phase plug (32 A) ........ 22kW
By the displayed values you can find out, that most effective charging by alternating current is by AC charging station utilizing 3x230V and maximum current of up to 32A on each phase, which is equivalent of 22kW.
AC CHARGING STATIONS
These chargers will maintain necessary communication with control system of the vehicle and provide charging for the safe conduct of the operator and vehicle. It is in fact interface, which allows safe and controlled interconnection of the onboard charger with the power network and trasfer up to 22kW of power per hour which is then transormed into direct current and sent to the battery. The performance of onboard charger is limiting however how much power it could actually use, regardless the performance of the charger.
Therefore, if the electro car posses only 3,7 kW onboard charger, then it doesn't matter if we connect the car to single phase socket using portable "smart cable" charger or if we connect it a 3-phase 22kW wallbox, because the onboard charger cannot utilize more than 3,7kW of power. If you need to charge faster, you are then required to charge at DC charging stations.
DC CHARGING STATIONS
Charging straighten using direct current, so called "rapid charging" or "DC charging" is done at DC charging stations, which can transform alternating current (AC) to direct current (DC) itself, then it bypass the onboard charger of electro car and send this direct current directly to the battery. This process is precisely controlled by the instructions and parameters of charging and battery control system. Charging is therefore not limited, by the performance of the onboard charger and you can charge at significantly faster rates.
Such charging station is technologically much more complex and many times more expensive than AC Charging stations, require high powered electric supply point and therefore we find them much less often than AC Charging stations.
And at the very end you have here an overview of all rechargeable electric connectors according to current standards.