The charging of electric vehicles

There are many different charging columns, but what are their differences?                                                                                                                   Classification of terms such as alternating current, direct current, fast and normal charging points and many more.

Electric vehicles are usually supplied with electricity via charging stations. A charging station can be compared to a petrol pump of conventional fuels, which is why it is also called an electric filling station. They represent the anchor point in the mobility and transport transition, which is why they can be considered extremely relevant. With regard to charging, there are various differences in terms of electricity and plug types.

1. Type of electricity

Two different charging pole models can be assigned to European electric vehicles. A distinction can be made between two types of charging, whereby these are referred to as AC (normal charging points with alternating current) and DC (fast charging points with direct current). The accumulators used in electric vehicles only work with direct current, which is why they can only be charged with direct current. For charging with alternating current, the type of current that occurs most frequently in the voltage grid, a conversion is necessary. This is done with a rectifier, which is called an on-board charger and is integrated in the vehicle. The difference between the two types of charging (AC and DC) is where in the charging process the conversion takes place. If the conversion takes place in the car itself, it is called AC charging. If, on the other hand, the conversion takes place in the charging station, this is referred to as DC charging. This means that no additional rectifier is needed in the vehicle. The rectifiers in a charging station can be significantly larger and thus convert more current than the on-board chargers installed in the vehicle. Depending on the type of current used for charging, a different maximum possible charging power can be achieved. These and many other differences between the two types of current must be taken into account when choosing a charging pole.

AC current, which is also referred to as "alternating current", is the type of electricity commonly used in households and is typically found in low-voltage networks in Europe. In addition, this current can be used to charge electric vehicles. However, the alternating current cannot be stored directly in the battery in the car, which is why an on-board charger converts the alternating current from the grid into direct current. The conversion allows the electricity to be stored and used in the vehicle batteries. Depending on the on-board charger installed, the charging power is limited to a maximum of 43 kW, which is why mainly AC charging columns are used as wallboxes in private use. Due to the low charging power, charging must take place over a longer period of time, which is why customers at home are more flexible with regard to the charging process. Due to the financial framework and the size of the on-board charger installed in the electric vehicle, the maximum possible current conversion in the car is the limiting factor here.

1.2 DC current

The second type of current is DC current, which stands for "direct current". In contrast to AC charging, the current does not change direction during transmission because there is no change in polarity. This is possible because the transformation from alternating current to direct current is not carried out in the car, but directly in the charging pole. As a result, the charged current is passed directly to the vehicle's batteries. This faster alternative to AC charging enables high charging powers of up to 300 kW, which is why the charging process is completed in just a few minutes. For this reason, DC fast charging stations are found where there is only a short standing time, for example at petrol stations. For private use, however, DC charging columns are not an economically relevant alternative, as the investment and subsequent installation are associated with high costs. In addition, a considerable power output of up to 500 amps is required, which is why the charging process must be well secured. If used improperly, for example, it can lead to overheating of the battery or a cable fire. Furthermore, private households cannot provide this charging power, as usually only 63 amps are available. Due to these aspects, fast charging stations tend to be installed in public spaces.

2. Plug types

As there is no standard plug for electric cars, there are a large number of different plug types on the market. These vary in terms of charging time and charging power. Since the car is charged more quickly at a higher charging power, the plug has a direct influence on the charging time. Only by looking at all the different plug types can an informed decision be made as to which electric car or charging pole is the most suitable, as compatibility with all plugs is not given. An overview of all relevant plug types is provided below.

2.1 SchuKo

With a SchuKo plug, where this stands for "Schutz-Kontakt-Stecker - translated: protective contact plug", emergency charging can be carried out from home. For this charge, the emergency cable is used, which is connected to the car with a type 2 connector and to a standard household socket. In this case, the "in-cable control box" (ICCB) takes over the control and communication. With this system of plugs (CEE 7/4) and sockets (CEE 7/3), a standard socket, which is common in Germany and Europe, can be used for short-term charging. In theory, a household socket with 230 volts could transmit an alternating current of up to 3.7 kW. In order to protect the equipment such as cables from overloading and destruction (e.g. cable fire), the charging power is reduced to approx. 2.3 - 2.6 kW, which results in a longer charging time. However, this charging power is perfectly sufficient if the e-vehicle is charged overnight, for example. On average, a range of 100-150 km can be recharged within 10 hours.

2.2 CEE plug

The blue, single-phase CEE plug is mainly used for connecting mobile homes on campsites, which is why it is also called a camping plug. With this plug, in contrast to the SchuKo plug, there is no danger of the cable burning, so longer charging times are not a problem. This allows charging at 230 V and 3.7 kW until the battery is fully charged. As a rule, however, a wallbox is connected with another more powerful plug version, which is why the relevance of the CEE plug cannot be considered very high.

2.3 Type 1 plug

The type 1 plug is a single-phase plug for alternating current, where the charging power is limited to max. 7.4 kW. This plug is mainly used in North America and Asia, which is why it is not very relevant for the European market. Due to the low demand in Germany for charging stations with type 1 plugs, adapters are automatically supplied with cars from Asian manufacturers. This means that charging can take place at standard charging stations despite the different plug types. However, this form is not future-proof because, in addition to the low charging power, no interlocking is possible.

2.4 Type 2 plug

The type 2 plug is a three-phase plug for alternating current, which allows the current to flow faster than with the single-phase plug (type 1 plug). The type 2 plug was defined by the European Commission in 2013 as the standard for charging e-vehicles at charging stations. For this reason, the suitable connector is installed by almost all major European manufacturers. Depending on the size of the on-board charger and the charging station, charging can be carried out at different power levels. For example, in the private sector, a maximum charging power of 11 or 22 kW (32 amps) is possible with a wallbox. This is very advantageous, as no great technical effort is required to charge the e-vehicle with a type 2 plug. At publicly accessible charging stations, charging is even possible with a power of up to 43 kW (63 amps). However, this is not the rule because, in addition to the cable, the on-board charger installed in the car is also a limiting factor.

2.5 ​CCS plug

The CCS plug (Combined Charging System) is an extension of the Type 2 plug with two additional power contacts, which is why it is also known as the "Combo 2 plug". This plug corresponds to the European standard, whereby the charging method and the plug variants are standardised. This combination plug can be used to charge with direct or alternating current, as the connection is divided into two areas. The upper section is a Type 2 connector, which can be used for charging with alternating current, and the lower section is used for charging with direct current. Because of this structure, a CCS connector can be used with two different connector types (DC or AC cable) when the connector is in the car. However, if the CCS connector is installed in the charging pole, charging is only possible with the associated cable. The maximum power is determined by the design and characteristics of the battery, which is a limiting factor. In addition, the charging status and the temperature have an influence on the charging power, which may be reduced as a result. The highest possible output at charging stations is currently 450 kW, and the trend is rising. However, as the car batteries are the limiting factor, normal charging points with 50 kW and fast charging points with up to 160 kW can be found in practice.

2.6CHAdeMO plug

The name of the CHAdeMO plug comes from "CHArge de Move". The plug was developed by Tepco, a Japanese energy company, together with various Japanese vehicle manufacturers. This direct current fast charging system enables a charging power of up to 100 kW, although in practice only a power of 50 kW is found at the charging stations. It is predominantly Japanese cars and older models that are equipped with a CHAdeMO connector. The plug is also compatible with some Tesla models, although an additional adapter is required. However, European charging stations increasingly rarely support this plug connection, as current developments show that the CSS plug will displace the CHAdeMO plug in the long run.

2.7 Tesla Supercharger

Tesla vehicles, which originate from the predecessor models and were intended for the European market, have their own type of plug. This Supercharger from Tesla is similar to the Type 2 plug, but the arrangement of the pins is slightly different. This plug can be used to charge at Tesla charging stations with up to 145 kW direct current. Even the Tesla "Model 3" vehicle series can charge up to 250 kW at the new "Supercharger V3" charging station model. However, only vehicles of the Tesla Motors brand can use these charging stations. Due to an internal switching of the plug assignment in the vehicle, however, charging is not only possible at Type 2 charging points, but also at DC fast charging points.

3. Summary

The charging station and the battery in the case of DC charging, or the maximum possible power to be supplied and the on-board charger in the case of AC charging, are the two limiting factors in the charging of electric vehicles. It can be concluded from this that the maximum possible charging power also depends on the plug type and the type of current. In addition, the customer's respective charging situation must also be taken into account when making a decision. The longer the charging time, the more sensible an AC charging pole is, although its charging power is much lower compared to a DC charging pole. However, the costs for installation and operation are significantly lower, which is why it is mainly found in the garage of private individuals. DC charging columns, on the other hand, make more sense for shorter parking periods. Due to the high charging capacity, these charging columns are often found at motorways, petrol stations, supermarkets and restaurants.

In addition, the state subsidises the expansion of the charging infrastructure within the framework of various subsidies in order to promote the traffic turnaround through the electrification of the transport sector and the reduction of CO2 emissions. This is also a reason why the relevance of fast charging stations is steadily increasing.

If you have any questions on the topics of AC and DC charging as well as the various plug types, please do not hesitate to contact us.