Innovative solutions are becoming increasingly available to make electric mobility mass-market-capable. An important part of this is the charging technology. In this context, the term smart charging is used for charging systems of electric or hybrid vehicles according to standards like ISO 15118 and DIN SPEC 70121.
In this know-how section essential knowledge about charging interfaces is presented.
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The CP is used for communication (exchange of control signals) between the EVSE and the EV. Using a 1 kHz square wave at ±12 V between the CP and PE line, the amplitude can be manipulated by the EV to control charging (PWM communication).
Proximity Pin / PlugPresent
The PP can prevent movement while the EV is connected to the EVSE. The electric vehicle can only drive away when the charging plug is unplugged. In the Type-2 connector the PP is used for a detection of the charging cable load capacity. Both the charging station and the electric car can use the PP contact to see how much the connected charging cable may be loaded. In the Type-1 connector this pin is used for manually unlocking the plug.
In older standard versions the PP of the Type-1 AC plug is called Connection Signal (CS) in IEC 62196 and Proximity Detection (PD) in SAE J1772.
The PE is a line that is earth grounded on the EVSE side. It is a way to deliver current to the earth in order to prevent electric shocks and it is used as reference pin for CP and PP.
It’s possible to charge EVs with alternating current (AC) and direct current (DC). Since the power that comes from the grid is always AC, it is necessary to convert AC to DC, because EVs can only store power as DC. For AC charging, the converter is built inside the EV. With the "on-board charger", the current is converted to DC inside the EV and then fed into the car’s battery. It is currently the most common charging method for electric vehicles.
Conductive AC charging capacity: up to 44 kW with a Type-2 connector
EVSE Connector Faces for AC Charging
AC Type-1 and Type-2
The IEC 62196-2 Type-1 connector is based on the SAE J1772 standard, designed for single-phase alternating current from 6 to 32 A and thus allows charging capacities of up to 7.4 kW. The IEC 62196-2 Type-2 connector was developed for three-phase alternating current up to 63 A, i.e. charging capacities up to 44 kW. A single-phase charging process can also be carried out via the Type-2 connector, in this case the contact pins L2 and L3 are not used. Therefore, it is easy to adapt between Type-1 and Type-2 plugs.
The AC GB/T 20234.2 standard enables both single- and three-phase charging in charging mode 3. It is built up analogous to the AC Type-2 plug.
A Tesla is charged with AC and DC superchargers, but in the EU, it is also possible to charge the EV with a three-phase AC Type-2 charger.
Unlike AC chargers, the converter for DC chargers is located "off-board", e.g. inside the charging station itself. That means it can feed power directly to the car's battery. This method enables very fast charging, which is why it will play a major role for EV fleet vehicles, such as electric buses, pool cars, logistic and transport vehicles.
Conductive DC charging capacity: up to 400 kW with a CCS Type-2 connector (CharIN is currently developing a megawatt charger with up to 3 MW)
EVSE Connector Faces for DC Charging
AC and DC charging plugs have different pins, which is why separate AC and DC inlets are required in the vehicle. For DC charging, the communication protocol is defined by GB/T 27930. It is used exclusively in China.
Similar to GB/T, CHAdeMO 2.0 uses CAN for the DC charging communication. It is used in Japan and mainly by Japanese OEMs outside of Japan.
The new CHAdeMO specification 3.0, the so-called ChaoJi (a harmonization of GB/T and CHAdeMO), was published in 2020. This version additionally offers up to 500 kW and a GB/T compatibility, as the plug was developed together with the GB/T charging standard.
The Tesla Supercharger uses a proprietary communication protocol which enables the charging process. In the EU, Tesla has switched to the CCS Type-2 connector face, because of the 2014/94 EU standard.
Combined Charging System
CCS Type-1 & CCS Type-2
The Combined Charging System (CCS) is the extension for the AC Type-1 and Type-2 plug for high DC charging capacities, which additionally has two large power contacts. Compared to the AC versions, the CP, PP and PE pins are also used, and the plug is expanded by positive and negative contacts. For a high-level communication for smart charging, a powerline communication (PLC) is overlaid on the CP.
External Identification Means (EIM)
EIM is an identification method that requires additional user interaction or other identification operations. This can be a smartphone app, credit card, RFID card or a license plate scanning at a charging station.
With this user-friendly authorization method, the EV is authorized using its vehicle ID. When the EV is connected to the charging station with the charging cable, the EV sends its media access control (MAC) address to the charging station. The charging station uses an open charge point protocol (OCPP) request to send the data to the charging station management system (CSMS) where the address is matched with an address list. A successful match sends an authorization response back to the charging station and an unsuccessful match sends an error state. Autocharge is mostly used in closed charging depots rather than at public charging stations, due to security concerns.
Plug and Charge (PnC)
The Plug and Charge authorization technique only requires the driver to plug the charging cable into the EV and the EV will be automatically identified and authorized to charge. The method works with an asymmetric key algorithm, that uses a key pair with a private and a public key. Both keys are linked in such a way that an encrypted message can only be decrypted with the corresponding key. The implementation of the public key infrastructure (PKI) and the certificate handling is required.
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Electric Vehicle Charging Communication Know-How Chart in DIN A1 format, folded to DIN A4
Order the Vector Electric Vehicle Chart. The clearly structured Poster in DIN A1 format gives you important technical details on Charging Communication. Among other things, the unique poster illustrates the following topics: