Charging electric vehicles


  • Preface
  • Charging plugs and connections
  • Electronic Vehicle Supply Equipment (EVSE)
  • Charging options
  • Loading times
  • Prices to load
  • Communication between charging station and vehicle
  • Proximity pilot
  • Control Pilot
  • Electricity network

The batteries of electric vehicles or plug-in hybrids can be charged with external charging facilities. You can connect the car with a charging cable to a public charging station, public charging station or your own wallbox (on the outside wall or in the garage) to charge the battery via the power grid. There is also often a mobile charger available with which you can charge via the socket, but it is recommended to use this charger only for emergencies.

The following image shows charging an electric car. On the side of the vehicle is a valve that looks very similar to a fuel filler flap on an internal combustion engine car. Behind the cover we find the plug connection into which the charging plug can be inserted.

The sticker in the cover indicates which color the LED next to the plug will light up at a certain status.

Charging plugs and connections:
The charging plugs and connections are standardized in Europe. For AC charging (alternating current) we know the Mennekes (type 2) and for DC charging (direct current) the CCS2 plug.

The following image shows a combined Mennekes Type 2 with CSS2 charging plugs. With this plug it is possible to (fast) charge with direct current.

The picture below shows the plugs used in other parts of the world. A distinction is made between AC and DC, with the DC variant often being an extension of the AC connector.

Electronic Vehicle Supply Equipment (EVSE):
Public charging facilities are always provided with an interface with EVSE (Electronic Vehicle Supply Equipment). This ensures security and communication. The functions of the EVSE include:

  • Checking connections: after a confirmation that all plugs are connected and locked, the charging mode starts;
  • Self-diagnosis: When detecting faults, the mains supply is interrupted;
  • Leakage current detection: with any form of leakage current, the mains supply is interrupted;
  • Current Control: Communicates with the on-board charger in the car using a PWM signal to limit the current.

Charging options:
When charging with alternating current (AC), the electricity from the grid in the car is converted to direct current (DC). The disadvantage of AC charging is that there is a high probability of induction phenomena and losses due to the conductor resistance. A conversion from AC to DC also takes place in the car before the energy reaches the battery, so that the charging current is limited.

Charging direct current (DC) allows “super” charging. AC/DC conversion no longer takes place in the on-board charger, but outside the vehicle. The battery can therefore be charged with a greater charging capacity and is therefore full faster. This is ideal for charging along the highway during a coffee break before continuing the journey.

We can divide the ways and speeds at which a vehicle can be loaded into four different modes. Mode 1, 2, 3 and 4 indicate how the vehicle is connected to the power point.

  • Mode 1: charging takes place directly via the electricity grid of a household connection. In the vehicle, the voltage is converted from AC (alternating current) to DC (direct current). The charging device provides security because there is no current limit or feedback from the vehicle to the power outlet. This way of charging is hardly used, because there is a risk of danger and defects, and is therefore prohibited in many countries.
  • Mode 2: As in mode 1, the wall socket of a house connection is used and the charging current is limited to 16 A with a capacity of 3,68 kW. However, to prevent overloading, the power is usually limited by the charging cables to 2,3 kW (approx. 10 A). With charging mode 2, the charging station is designed as a mobile charger, which can be taken along. In the vehicle, the on-board charger converts AC into DC.
  • Mode 3: a fixed charging station or wallbox is used for charging, which is connected to the electricity network of a building, just like in mode 2. The mode 3 charger is suitable for AC charging and for powers from 3,68 to 22 kW. Again, the AC is converted to DC in the vehicle's power electronics.
  • Mode 4: While charging modes 1 to 3 charge with alternating current and must be converted to direct current in the vehicle, with mode 4 charging, the conversion from alternating current to direct current takes place at the charging station itself. The direct current is supplied directly to the battery pack. This is known as DC charging or as fast charging. A DC charging station for mode 4 charging requires an input voltage of at least 480 volts and supplies power from 43 kW. 
Fast charging station

Loading times:

The charging times of hybrid and electric vehicles can be determined by dividing the battery capacity by the power supplied by the charger.
The available charging capacity is not only determined by the type of charger and charging cable, but also by the maximum charging capacity for which the power electronics in the vehicle are suitable. New luxury cars get an increasingly larger battery with more capacity for a longer range, but because the charging capacity increases, it can even mean that the charging time decreases. As an example, we take a VW e-Golf (32 kWh) versus a Mercedes EQS SUV 500 (108,4 kWh). Not all vehicles can charge to 100% with DC. DC charging stops at 80%. The last 20% go with a lower charging power via AC. This is to protect the HV battery.

VW e-Golf (32 kWh)

AC charging:
With a Type 2 charging plug, the battery pack can be charged via AC. The maximum charging capacity of the on-board charger is 3,7 kW. When the battery pack is charged from 20% via a charging station (mode 3), this takes approx. 7 hours. Explanation: 80% (loading) of 32 kWh = 25,6 kWh. We calculate the charging time by dividing the required power by the power supplied: (25,6 / 3,68) = 6,96 hours (6 hours and 58 minutes).

When charging via the socket (mode 2), the power is limited to 2,3 kW and the charging time is 11,13 hours (11 hours and 8 minutes). 

DC charging:
With fast charging via direct current with a capacity of 44 kW, the battery is fully charged after 0,58 hours (35 minutes).

Mercedes EQS SUV 500 4MATIC (108,4 kWh)

AC charging:
With a Type 2 charging plug, the battery pack can be charged via AC. The maximum charging capacity of the on-board charger is 11 kW. Again we assume that we will charge from 20%. The power to be supplied by the charging device is 86,72 kW. With charging via the charging station, the charging time is 7,88 hours (7 hours and 53 minutes).

DC charging:
With mode 4 it is possible to charge up to 207 kW. The charging time is: (86,72 / 207) = 0,42 hours (25 minutes).

Prices to load:
There are many providers of charge cards. Various websites offer overviews with the rates. In this section, we assume the energy rates that applied in March 2023 and do not take into account subscription fees or starting rates per charging session, but only energy prices.

  • The Netherlands AC €0,60/kWh
  • Netherlands DC €0,85/kWh
  • Belgium and Luxembourg €0,65/kWh
  • Europe: AC €0,51/kWh
  • Europe: DC €0,87/kWh 

In the examples of the VW e-Golf and the Mercedes EQS, we calculate the charging prices based on the charging capacity and the fact that we charge from 20% range.

  • VW e-Golf: assuming the charging capacity of 25,6 kW, it costs €15,36 for AC charging in the Netherlands, €21,76 for DC charging. Total range: 190 km.
  • Mercedes EQS: with a charging capacity of 86,72 kW, it costs €52 in the Netherlands for AC charging and €73,70 for DC charging. The range is around 485 km.
To calculate what it costs to charge from 0 to 100%, the total charging capacity (usable battery capacity) must be multiplied by the price per kWh. The prices of the e-Golf and the Mercedes will then be 20% higher. However, it should be taken into account that not all HV batteries above 80% can be fully charged with DC.

Communication between charging station and vehicle:
The charging interface module provides communication between the charging station and the vehicle. Via the so-called “Proximity Pilot” and the “Control Pilot”, abbreviated as “PP” and “CP”, it is indicated that a charging plug is connected, and it is determined how much charging current is allowed. The operation of the PP and CP is explained in the next two paragraphs.

In the picture we see the CP and PP in the American Type 1 (left) and European Type 2 Mennekes plug (right), both combined with the DC charging plug. We concentrate on the right plug with the CP, PP, the three phases (L1 to L3) with neutral wire (N) and the so-called Protective Earth (PE).

This section uses the following scheme, which is based on the European standard (IEC 62196-2). This concerns the Type 2 connector, also known as the Mennekes. In the diagram we see (from left to right) the following components:

  • EVSE controller: this is the module that is built into the charging station or wallbox;
  • Charging plug: in addition to the charging current, communication takes place via the PP and CP between the EVSE controller and the vehicle controller;
  • Vehicle controller: the electronics in the vehicle activate the charging process as soon as several conditions are met.
Scheme controller, charging plug and vehicle controller (European Type 2)

Proximity Pilot:
The proximity pilot has two functions: registering whether a charging cable is connected and registering which type of charging cable is connected, so that the maximum charging current can be determined.

In the diagram below, the circuit of the PP is colored red. Here we see a voltage divider between R1 and R2, which is powered by 5 volts. The control unit measures the voltage between R1 and R2 (marked with a voltmeter for clarity). Resistor R1 serves as a pull-up resistor. 

  • If no charging plug is connected, there is no voltage divider. Resistor R1 takes no voltage, so the measured voltage is 5 volts;
  • When the charging plug is connected, a series connection is created. With the given resistor values, the control unit will measure a voltage of 3,1 volts.
Scheme controller, charging plug and vehicle controller (European Type 2)

The resistance value in the charging plug indicates the maximum current allowed through the charging cable. These resistor values ​​are as follows:

  • 100 ohms: 63 A maximum;
  • 220 ohms: 32A maximum;
  • 680 ohms: 20 A maximum;
  • 1500 ohms: 13A maximum.

The resistance value in the example is 220 ohms, which means that the current through this charging cable may not exceed 32 A. A higher or lower resistance results in a different voltage division and therefore a different input voltage for the controller.

The North American connectors are covered by the standard: SAE J1772. This Type 1 charging plug differs from the European version:

  • Single-phase AC voltage instead of three-phase AC voltage in the European Type 2 plug;
  • Manual locking hook. The extra voltage divider makes it possible to build in extra safety. As soon as it recognizes that the button has been pressed, the charging system switches off immediately.

The diagram below shows the US version.

In particular, the locking hook extends the Proximity Pilot circuit.

  • There is a voltage divider in the connector;
  • Switch S3 is parallel to resistor R7. At rest, the switch is closed and resistor R7 is bridged;
  • When removing the plug, the driver must operate the locking hook to pull the plug out of the vehicle. While pressing this hook, S3 is opened. Resistor R7 is part of the voltage divider.
Scheme controller, charging plug and vehicle controller (US Type 1)

Control Pilot:
The CP monitors the charging process from the request to start charging, to the end of charging when the battery is fully charged. The CP enables communication between the EVSE controller in the charging device and the vehicle.

  • After connecting the charging cable to the charging station, the EVSE controller applies a voltage of 12 volts to the Control Pilot connection of the charging plug.
  • as soon as the charging plug is connected to the vehicle, the voltage drops to about 9 volts due to the voltage divider between R3 and R4;
  • via the ST2 (Schmitt trigger) the controller measures the incoming voltage.

The current flow with connected charging cable is marked in red.

Scheme controller, charging plug and vehicle controller (European Type 2)
  • After registering 9 volts, the EVSE controller energizes relay K2. Instead of the 12 volt supply, the oscillator is included in the circuit;
  • the oscillator produces a square-wave voltage from -12 to +12 volts;
  • the diode causes the voltage on the CP terminal to alternate between +9 and -12 volts;
  • with the duty cycle in the PWM signal, the EVSE controller indicates the maximum charging current that the vehicle is allowed to use.
Scheme controller, charging plug and vehicle controller (European Type 2)

After establishing the PWM signal, the vehicle controller turns on relay K1 as soon as the vehicle is ready to start charging.

  • Relay K1 switches resistor R5 to ground;
  • due to the parallel connection between R4 and R5, the positive pulse of the PWM signal drops to 6 volts;
  • The voltage of 6 volts is measured by the EVSE controller in the charger and now connects the power supply to the charging cable to charge the battery.
Scheme controller, charging plug and vehicle controller (European Type 2)

The image below shows the signal from the Control Pilot, showing the voltage development against time. This voltage development can be measured on the Control Pilot connection of the charging plug, while it is connected.

  • Status A: There is no connection to the vehicle. As long as no charging cable is connected, the voltage remains 12 volts;
  • Status B: Electric Vehicle is connected. Relay K2 is energized. The voltage drops to 9 volts due to the diode in the circuit;
  • Status C: Relay K1 is energized. This is “the signal” for the charging unit to start the charging process.

Status D and E indicate when an action is required for ventilation, or to end the charging process due to an error being detected.

Electricity network:
Modes 1 to 4 were shown in the “load options” section. You can choose to charge the vehicle at home via the home charger, wallbox, charging station or via a fast charger along the highway. In particular, charging at home via your own charging facility is becoming increasingly popular. A home charger can simply be connected to a socket, but in order to obtain the shortest possible charging time with more charging current, a personal wallbox can be connected by adjusting the group cabinet. First we look at the concepts: 1- and 3-phase alternating current.

With a 1-phase connection we see a “standard” electricity cable with three cores:

  • brown: phase wire;
  • blue: neutral wire;
  • yellow/green: ground wire.

With a 1-phase charging station or wallbox, the electricity goes through two wires (the phase wire and the neutral wire)

A 1-phase wallbox or charging station uses the standard 230 V connection of the home electronics. The maximum power is 16 A, which brings the maximum charging power of a 1-phase charger to 3,7 kW. A battery pack of 60 kW is charged with this charging capacity in about 16 hours, which takes a relatively long time. Most new electric cars have a higher capacity.

It is possible to increase the maximum current in the group box of the home electronics, so that there is more capacity for a 32 A 1-phase charger. In that case, a maximum of 7,4 kW can be charged. However, with a 1-phase charger there is a chance that the group box will become overloaded, resulting in a power failure. After all, in addition to a charging station, there are more electrical appliances that use the electricity network, including the washing machine, dishwasher, hob and heat pump. With the help of load balancing, the maximum capacity can be used:

  • during the day there is a good chance that several electrical appliances are used. The charging current for the vehicle is reduced;
  • most devices are switched off at night, so that the vehicle has more charging capacity.

To charge faster, it is possible to connect the charging station or wallbox to the group box via a 3-phase connection. This does not necessarily have to be power current. With a 3-phase connection we see two extra wires:

  • black: extra phase wire;
  • grey: extra phase wire.

With a 3-phase charging station, the electricity goes through four wires (the three phase wires and the neutral wire). 
The charging capacity of a charging station or wallbox on a 3-phase connection is higher than with a 1-phase, so that the vehicle charges faster. The maximum charging current of the vehicle is never exceeded. Some vehicles are only suitable for charging up to 3,7 kW. It makes no sense to create a 3-phase connection. Vehicles can also be suitable for 7,4 or 11 kW: it pays to increase the capacity (3 * 16 A) from the group cabinet.

In older houses we often see a 1-phase connection (up to 35 A) in the group box. All three phases are present, but only one is connected.
The group box can be converted so that all three phases are used. Newer houses, where the group box is prepared for more electrical consumers (such as solar panels, an induction hob and a heat pump), can already be equipped with a 3-phase connection from the moment of delivery. In that case it says “3×220/230V or 3×380/400 volts” on the electricity meter. There are also a total of four wires - the three phase wires and the neutral wire - coming out of the bottom of the distribution box. Depending on the group box, the group is protected up to 1x25A, 1x30A or 1,35A. The greater the listed amperage, the more current can be used at a time.

The figure below shows five situations from a 1-phase to a 3-phase connection in the group cabinet and the use of a 1-phase or 3-phase charger.

1 phase: With the emergency charger you can charge the vehicle via the socket. With a wallbox you can charge up to 1A with a 16-phase group without load balancing, and 32A with load balancing. The 32A can only be achieved when no other consumers are active in the house.

For capacities up to 7,4 kW, a 1-phase network with load balancing is possible. When using multiple electrical appliances with a high consumption in the house, including the washing machine / dryer, dishwasher and heat pump, the power will decrease to protect against overload. In practice, this means that the power can decrease by up to 50%. The switch from 1- to 3-phase is therefore wise.

3 phase: When too much power is demanded at the same time, this can cause overload and the protection is activated, causing the power to fail. It is therefore important that the network can supply sufficient electricity. With a 3-phase connection, more current can be supplied at the same time. By default, the 3 phase groups are protected up to 25A.

  • 11 kW: reinforcement of the meter cupboard is necessary. The adjustment from 1 phase to 3 phase is sufficient;
  • 22 kW: in addition to the adjustment from 1 phase to 3 phase, a reinforcement of 35A is required.

The adjustment to 22 kW and 35A is hardly interesting for private individuals. Due to the weighting, additional annual standing costs of € 1000 must be paid. For each heavier step (3x63A or 3x80A) an additional payment must be made. In addition, many electric vehicles are not (yet) suitable for charging with such high alternating currents:

The number of vehicles that can charge 22 kW on AC is expected to increase in the coming years.

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