EV charging station design

From Electrical Installation Guide
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The term “EV charging station”, as defined by IEC 61851-1, is the stationary part of the EV supply equipment that is connected to the supply network. It can be either wall-mounted or floor standing, AC or DC. It is dedicated equipment for charging EVs through Mode 3 (AC) and Mode 4 (DC).

The following paragraphs provide details on the design and characteristics of EV charging stations in mode 3 and mode 4.

Charging station design – IEC standards

Charging station in mode 3 and mode 4 must be compliant with standard IEC 61851.

This standard covers the mechanical, electrical, communications, EMC and performance requirements for electric vehicle supply equipment in mode 3 and mode 4.

Part 1 of this standard covers the general requirements, which is the basis for all subsequent standards in the series. It includes the requirements for AC charging stations. Edition 3 of this standard will be mandatory by February 2022 in the European Union.

Part 21-2: covers the EMC requirements for off-board electric vehicle charging systems which defines whether the charging station is Class A or Class B.

Class A off-board electric vehicle charging systems are equipment that are suitable for use in all locations apart from residential, as well as those directly connected to a low voltage power supply network which supplies buildings used for residential purposes.
Class B off-board electric vehicle charging systems are equipment that are suitable for use in residential establishments as well as in establishments directly connected to a low voltage power supply network which supplies buildings used for residential purposes.

Part 23 covers the requirements for DC charging stations that are both permanently wired, and plug connected.

Part 24 covers digital communication between a DC charging station and an electrical vehicle for control of DC charging.

In general, the main characteristics of the charging station depend on usage and on the location where it is installed.

Charging station design - Mode 3 and Mode 4 common characteristics

Environmental characteristics

Charging station can be installed indoors or outdoors.

As a general rule, IP protection is at least IP54 for outdoor usage even if IEC 61851-1 recommends only IP44. Shock IK protection is generally IK10. To be IEC 61851-1 compliant, the charger must be able to operate up to 2000 meters altitude and to a minimum temperature of at least -25°C in outdoor environments and -5°C for indoor environments.

In practice, charging station can usually operate within a range of -30°C to +50°C and within a relative humidity range of 5% to 95%.

Charging station output

Charging station output is called socket-outlet where there is no attached cable, and is called electric vehicle connector where there is attached cable.

Charging station can feature single or multiple output. In the case of AC charging station, single output is usually used for single-family individual house. Multiple output is usually used for chargers installed in public car parks. Outputs can be of the same type or different type.

The advantage of having several outputs is that the user can potentially charge several electric vehicles at the same time. In which case, the charging station can either share its total power between each of the outputs or it can have dedicated full power for each output, independently of the other outputs. However, it is possible that a charging station with several outputs is unable to manage several charges simultaneously.

It is also possible that a charging station can include a combination of DC and AC output.


Fig. EV19 – Example of charging station with authentication mechanism

Where the charging station is located in a public space, it may feature an authentication mechanism, for example a RFID reader. Such a mechanism allows identification of the charging station user, which will determine whether or not to authorize him to use the charging station, or whether or not to charge him for its usage.

It is also possible to allocate different privileges to different users; for example, giving priority to VIP users, so that they can charge their electric vehicle, where there is a multiple output charging station.

Authentication can be managed in a different way - for example, it can be managed locally or remotely through a third-party application. In the case of a third-party application, the charging station should be able to manage off-line (degraded) mode in case communication is lost with the remote application: for example, in off-line mode, the charge could be allowed to all badges, or only to the one present in the cache memory of the charger (last badges used), or to no badges…

A charging station that is installed at home usually will not require an authentication mechanism.

Charging station communication

Charging stations can function as standalone with no external communication, however they can also feature several types of communication modes - through Ethernet, Wi-Fi, 3G/4G, Bluetooth, NFC and even dry contact.

External communication can be used for a number of scenarios:

  • Configuration of the charging station (for example: configuration of RFID authorization management, parameters, etc…)
  • Maintenance (for diagnosis of any issues)
  • Remote authorization to charge (if charging station authorization is from an external system)
  • To receive command for power limitation (for example, receiving on-peak / off-peak hour signal from electronic meter or from a load management system)

Mode 3 charging station design

AC charging station - power and current delivery

Power delivered by AC charging station is 3.7 kW, 7.4 kW, 11 kW or 22 kW. The standard maximum current delivered is 32 A.

AC charging station - installation type

Two main types of AC charging station installation is possible - on wall or on floor.

Wall solution is convenient for installation in scenarios such as single-family individual houses.

Floor installation is made with a pedestal which supports one or several charging stations. Charging stations can also be embedded with a pedestal. This type of solution can be used for work place car parks for example.

AC Charging station - with or without attached cable

AC charging stations can either feature an attached cable or require the use of a separate cable. In some cases, local legislation requires the use of one solution or the other, like, for example the country of Singapore, where an attached cable is mandatory.

An AC charging station with attached cable is designed for scenarios where the same type of connection will always be used. For example, in a location where the charging station will always be used by the same vehicle.

An AC charging station without attached cable, is more flexible, because it is designed for any car. It includes, type 1, type 2 or type 2S connector, etc…or even a domestic plug. EV drivers use their own personal cable to connect from the charging station to their vehicle. In this scenario, there may be local regulations that demand the usage of a specific type of socket, as for example in France, where a type 2 connector for charging station is prohibited. Instead a type 2-S must be used.

This type of charging station, (with no attached cable), is used especially in commercial buildings where many different types of vehicles are charging at any one time.

Mode 4 Fast Charging Station design

Fast charging station - power delivery

Power delivered by DC charging stations ranges from 24 kW to more than 900 kW with a Combo CCS connector, and up to 400 kW with a CHAdeMO connector.

Fast charging station - installation type

Fast DC charging station power range can range from 24 kW to more than 900 kW. Therefore, the mechanical design of the charging station can vary significantly, from one to the next.

In general, however, we can put them into three main categories.

The first style, wall installation, is a good option for chargers around 24 kW. For higher power values, the weight of the charger increases, so the installation needs to be positioned on the floor.

The second type of design is centralized standalone chargers, which are floor standing.

The final category of charger consists of charging cabinet and one to several satellite charging poles. Inside the cabinet are power modules. In this way, the charging power can be dynamically distributed into each satellite pole. This type of solution is generally used for DC charging stations providing power above > 500 kW.

Fast charging station - attached cable

A fast DC charging station requires attached cables.