Principles of EV Charging Technology | Basic Knowledge about Charging Electric Vehicles

The transportation of the future follows various country-specific framework conditions.

Charging Standards and Connector Types

The common standards and mating faces

Internationally, three charging standards with their own specific geometries for charging connectors and charging sockets have become established – starting from North America, Europe, and China. In addition, the connector for AC charging (mode 3, cases B and C) has a different design than the one for DC charging (mode 4).

The Type 1 standard for North America does not provide for an infrastructure-side charging connector. In Europe, an adapter cable is used in this case, which consists of a Type 1 charging connector on the vehicle side and a Type 2 charging connector on the infrastructure side.

Where does which charging standard apply?

The current prevalence on the world map

AC and DC charging: What is the difference?

And what is recommended in which situation?

AC charging

The alternating current (AC) from the supply network first flows into the vehicle via the charging station and charging cable – controlled, but without conversion. Only an AC/DC converter installed in the vehicle, the so-called onboard charger, converts it into direct current (DC), which can be used to charge the battery. Because AC charging stations, therefore, do not require conversion electronics, they are usually less expensive than DC charging stations and more attractive for private applications. Depending on the charging station, charging cable, and onboard charger, charging powers of up to 22 kW can be achieved. Due to these comparatively low powers, AC charging is gentler on the battery and is always recommended when the vehicle is parked for longer than 30 minutes – for example, overnight in a carport, garage, or at a hotel, and during the day at restaurants and supermarkets.

DC charging

=Here, the power contacts and cable cross-sections of the charging connector are larger than for AC charging. Significantly higher charging powers of up to 500 kW (High Power Charging, HPC) can be transmitted, which significantly reduces charging times. Therefore, this is also referred to as fast charging or ultrafast charging. In contrast to AC charging, the power is converted from AC to DC in the charging station, where appropriate power electronics are installed. DC charging is therefore more complex and cost-intensive for this reason among others, and is predominantly used commercially. It is recommended for long driving distances with short breaks to recharge the range in a few minutes, for example at highway service stations.

What charging modes are there for AC and DC charging?

The charging process can be performed in different ways

AC charging with mode 1

The vehicle is charged with AC power from a household outlet. Voltages up to 250 V may be applied in single-phase grids, and up to 480 V in three-phase grids. The maximum charging current is 16 A. There is no communication between the vehicle and the charging point. Fuse protection via a residual current device (RCD) is a mandatory requirement.

AC charging with mode 2

As per mode 1, but the maximum charging current here is 32 A and the charging cable is equipped with an In-Cable Control-and-Protection Device (IC-CPD). This device includes residual current safety equipment (RCD), communicates with the vehicle, and thus controls the charging process.

AC charging with mode 3, case A

With mode 3, the vehicle is charged with AC power at a charging station or home charger in which the necessary residual current device (RCD) is already integrated. The charging station takes over communication with the vehicle. The vehicle can be charged in single-phase grids with up to 250 V and in three-phase grids with up to 480 V, with a maximum charging current of up to 63 A. Mode 3 is split into three cases:In case A, a charging cable permanently connected to the vehicle is used. Therefore, it only has a connector unit on one end: the infrastructure charging plug that is plugged into the charging socket on the charging station. Although case A is described in the standards, it is hardly ever used in practice today.

AC charging with mode 3, case B

Case B requires what is called a mobile AC charging cable that is carried in the trunk, for example. It has a connector unit at both ends: On one end, the vehicle charging connector is inserted into the vehicle charging inlet. On the other end, the infrastructure charging plug is plugged into the charging socket on the charging station. Case B is mainly used at public charging stations.

AC charging with mode 3, case C

Case C is the opposite of case A, because in this case the charging cable is permanently secured to the charging station. The other end of the cable has a connector unit – the vehicle charging connector – which is plugged into the vehicle charging inlet. Case C is very often used in the private sector.

DC charging with mode 4

This mode is the only one that describes DC charging at fast charging stations. Increased safety requirements apply due to the high charging currents of up to 500 A. Therefore, the charging cable is always permanently secured to the charging station in this case. A pluggable connection is only provided on the vehicle side – in the form of the vehicle charging connector, which is inserted into the vehicle charging inlet. Therefore, mode 4 is not split into three cases (as mode 3 is). Temperature monitoring of the power contacts in the charging connector and additional protective functions in the charging station, such as insulation monitoring, are also required.

What is the Combined Charging System (CCS)?

One universal charging interface for AC and DC charging

The special feature of Combined Charging System (CCS) is the CCS charging inlet in the vehicle, into which both AC and DC charging connectors fit. The electric vehicle thus requires just one charging interface for AC and DC charging.The mating face structure of the Type 1 and Type 2 charging standards follow the CCS principle. CCS Type 2 was declared the official charging standard for all of Europe by the European Commission back in 2013. In the meantime, our goal of establishing CCS as the global fast-charging standard has become a reality in large parts of the world. And more and more countries are adopting CCS.

What are the advantages of CCS in practice?

Flexible AC and DC charging via just one vehicle charging inlet | Vehicle manufacturers save on components, space, and costs | Highest degree of safety thanks to actuator interlocking and temperature monitoring | High acceptance and prevalence in large parts of the world

Charging plug locking

For maximum safety during the charging process

All CCS charging inlets are equipped with an electromagnetic locking actuator in accordance with the standards. This locks the charging connector into place laterally or directly on the locking clip in the mating face during the charging process.The actuator bolt is designed to withstand high pull-out forces. This makes it impossible to pull the charging connector out during the charging process. 

Precise temperature monitoring

Reliable protection against overheating

A safe charging process also includes monitoring the temperature in the CCS charging system. According to IEC 62196, heating must not exceed 105°C. Temperature-dependent resistance sensors, e.g. Pt 1000, therefore ensure fast and precise temperature measurement at the DC power contacts.The temperature values are communicated to the charging controller via corresponding signal outputs. If overheating occurs, for example, due to excessively high external temperatures or overloads, the charging controller can abort the charging process or derate the charging power.

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