EV Charging Knowledge Bank

Understanding electric car charging

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Charging point parameters

There are three main parameters associated with EV charging points:

  • rated power (in kW) and current type (DC / AC);
  • connector type;
  • mode.

Rated power and current type (DC / AC)

    The rated power is determined by the charge current (Amps) and the voltage. The current may be AC (alternating current) or DC (direct current). 
    The limiting factor in rated power is usually the grid connection - if you have a standard domestic single phase (230V) supply, you won't be able to achieve a charging rate of more than 7.4kW. Even with a standard commercial 3 phase connection, the power rating for AC charging is limited to 22kW. Greater charging power (50kW - 120kW) can be achieved with rapid DC chargers.
    The options for rated power are summarised in the following table. Note that most cars have a battery sized at between 10kWh and 40kWh (100 miles typically takes 30kWh plus).  Tesla models have a 75kWh to 100kWh battery. 
Supply Type / Charger Rating AC/DC Rated power* Time to charge 10kWh

Time to charge 30kWh

Regular electricity socket 13A Slow AC 3.0 kW 3 hours 20 mins 10 hours
Single phase 16A Slow AC 3.7 kW 2h 40 mins 8 hours
Single phase 32A Fast AC 7.4 kW 1h 20 mins 4 hours
3 phase, 16A per phase Fast AC 11 kW 55 mins 2 hours 45 mins 
3 phase, 32A per phase Fast AC 22 kW 27 mins 1 hour 22 mins
3 phase, 60A per phase  Rapid AC 43kW 14 mins 42 mins
3 phase, DC Rapid DC 50kW 12 mins 36 mins
3 phase, DC Rapid DC 120kW 5 mins 15 mins

 

*Simplistically (ignoring Power Factor correction):

for single phase 230V connections, Power (kW) = Amps (A) x 230V * 0.001;

for 3 phase 400V connections, Power (kW) = 1.732 * Amps per phase (A) x 400V *0.001.

Connector type

Electric vehicles are connected to the charger via a cable which must be fitted with connectors, one of which fits into the car inlet socket, and the second of which fits into the charger outlet socket.

Cables may be like laptop adapters - with connectors at either end, as in this picture:

EV charger cable.jpg

Alternatively, one end of the cable may be permanently 'tethered' to a charging unit.  The options are illustrated by the Rolec WallPod offering. The first image shows a unit with a tethered cable. The second shows a unit with a 'universal' Type 2 socket:

Rolec Mode 3 Tethered Lead.jpg Rolec Non-Tether WallPod.jpg

 

Note "Should I get tethered or untethered?" is one of the questions we get asked the most.

We have historically recommended universal socket chargers as it gives flexibility if you move say from a Type 1 (e.g. old Nissan Leaf) to a Type 2 vehicle - see below for an explanation of Type 1 / Type 2.  A lot of users however do prefer a tethered unit as it is so much more convenient - lifting the cable in and out of the car every time you want to charge it can become onerous after a while.

This is one of the reasons we recommend EVBox's Elvi. With Elvi you can buy a tethered charger and if you swap from Type 1 to Type 2 or vice versa, you can buy a replacement cable and swap it out yourself. There’s a security pin inside the unit that holds the cable in place.

With EO's untethered chargers you can get around the hassle of taking out the cable by simply leaving your car charger cable attached. This doesn't negate the access security, however you need to be happy to leave the charger cable trailing on the floor, or find your own way of securing it to the wall.

Charging standards

There is no harmonized charging standard and thus a few charging protocols have developed. More on these below.  

Whether or not a charger will be compatible with a given vehicle depends on the car. That said, most EVs are equipped with two or more cables to allow the use of chargers with different connector outlets.  These may allow charged by AC and / or DC. 

In particular it should be noted that most (all?) cars can be charged by connection to a 'Type 2' socket; even if they use a Type 1 inlet, they will be supplied with a cable for connection to a Type 2 socket - as with the Nissan Leaf example that follows. Hence the 'universal' Rolec WallPod above has a Type 2 socket, as indeed do all 'universal' charging stations.

An 'old style' Nissan Leaf 24kWh has two vehicle inlets as follows:

  • Type 1;
  • CHAdeMO.

It can be charged by a Type 1 AC inlet at a rate of 3.6kW (16A), which can be supplied using a slow (3kW) or fast (7kW /22kW) chargers. It can also be 'rapid charged' with a 50kW DC CHAdeMO inlet. 

Note that at the moment, as with the Nissan Leaf 24kWh, many plug-in vehicles are limited to charging at 16A, due to their on board charging capacity, but in future most vehicles will be able to charge at the much faster 32A rate.  The 7kW / 22kW charging station will not over power the vehicle - it has an on-board charge controller, which will regulate what it will draw. Thus, we always recommend installing a minimum of a 7kW charger in the home, even if the current car will only take 3.6kW.

Specifically, compatible chargers for the Nissan Leaf 24kWh are as follows:

Charger  Car Inlet type Charger Outlet type Cable
Slow 3kW (13A) Type 1 Standard 3-pin

Type 1 (J1772) to 3 pin

EV owner supplies cable

Slow 3.7kW (16A) Type 1 Type 2, no tethered cable

Type 1 to Type 2

EV owner supplies cable to EV charger with Type 2 outlet

Slow 3.7kW (16A) Type 1 Type 1 EV slow charger with tethered cable and Type 1 connector for car
Fast 7kW (32A) Type 1 Type 1 EV fast charger with tethered Type 1 cable
Fast 7kW (32A) Type 1  Type 2

Type 1 to Type 2

Ev owner supplies cable to EV charger with Type 2 outlet

Fast 22kW (32A) Type 1 Type 2

Type 1 to Type 2

Ev owner supplies cable to EV charger with Type 2 outlet

Rapid DC 50kW (125A) CHAdeMO CHAdeMO

Unit with tethered CHAdeMO DC connector.



To find out which connectors can be used by a particular EV model, we recommend you use Zap-Map’s Connector Selector.

Connector protocols

Connector protocols, and the achievable charge rates under each protocol are shown in the following table:

Protocol AC / DC Single phase/ 3 phase Charger Rating Achievable Picture
UK 3-pin (BS 1363) AC Single phase 13A / 2.3-3kW Plug.png
Type 1 American (J1772) AC Single phase 3-7kW Type 1.png
Type 2 European (Mennekes, IEC 62196) AC Single phase and 3 phase 3-43kW Type 2.png
Commando (IEC 60309) AC Single phase and 3 phase 3-22kW  
European Combined Charging System (CCS) DC - 50kW CCS.png
Japanese JEVS (CHAdeMO) DC - 50kW CHAEDEMO.png
Tesla Supercharger (Type 2) DC - 50-120kW Type 2.png

 

 

Which charger should I install?

 

Domestic

See Choosing a domestic charger for more information.

The minimum recommended installation for a domestic property is a 16A 3.6kW charger. It is perfect for 6-10 hour overnight charging. However, as mentioned above, we generally recommend you 'future-proof' and install a 7kW (32A) fast charger in your home.

Nearly all electric models can be slow charged with each vehicle being supplied with a charging cable with the appropriate connectors.

We recommend the following chargers for domestic installations:

  • eoMini or eoGenius - if necessary the eoGenius can be installed as a dumb charger and upgraded later;
  • EV Box Elvi, or HomeLine for leased cars as it facilitates easy reimbursement by your employer;
  • Rolec WallPod - budget charger;
  • zappi (good for homes with solar PV as excess solar can be diverted);
  • car-specific chargers (e.g. for Tesla, Porsche).

If you are set on a car model, you could install a unit with a tethered cable, suitable for that model. Otherwise it may be prudent to install a charger with a Type 2 'universal' socket and then purchase a connection cable as necessary for whichever car you are driving at a given time (or use the one supplied by the car).

Commercial: workplace charging or public space charging

 

See Choosing a Commercial EV Charger for more information.

Chargers installed in the Workplace should ideally have the following functionality:

  • payment mechanism and / or tracking of usage for employee benefits reporting;
  • universal connection;
  • remote management.

Additional options may be useful, as follows, depending on application:

  • pole mounting (reduces installation cost);
  • personal charging cards, key fobs, booking system;
  • configurable prices and charging windows;
  • pre-payment, 
  • custom branding
  • load management to avoid breaching grid import limit;
  • vandal proofing.

Our favourite charging brands are EO and EVBox, with chargers as follows:

  • eoGenius;
  • EVBox's BusinessLine and PublicLine.

Other terms you may come across: Slow vs Fast vs Rapid

You may come across the terms 'slow charging', 'fast charging' and 'rapid charging'.

Slow charging is defined as a single phase 13A or 16A charger. A 13A charger is in fact a charging adapter that plus into a standard 13A socket, usually operating at 11A.  

Fast charging is defined as 7-22kW charging, able to fully recharge most models in 3-4 hours. The required current is 32A.  Most commercal chargers use this model, as do most 'street' chargers.

Note that not all electric vehicles can accept a 32A fast charge. However they can still be connected to fast chargers (with the right connector), and will draw the correct current, according to their capability.

Rapid charging units operate at 43-120kW and will re-charge most cars to around 80% in 30 minutes.  They may supply the vehicle with DC (50kW - 120kW) or AC (43kW). They usually use a tethered cable equipped with a non-removable connector.  

As with fast charging, not all electric vehicles can use a rapid charger. While the short charge times make this option very convenient, regular use of rapid charging can reduce battery life. 

Other terms you may come across: Modes and Cases

 

Mode 1: Household socket and extension cord

The vehicle is connected to the power grid through standard 3 pin socket present in residences allowing a maximum delivery of power of 11A ( to account for overloading of the socket).

This limits the user to a lower amount of available power delivered to the vehicle.

In addition the high draw from the charger at maximum power over several hours will increase wear on the socket and increase the likelihood of fire.

Electrical injury or risk of fire are much higher if the electrical installation is not up to current regs or the fuse board is not protected by an RCD.

Heating of the socket and cables following intensive use for several hours at or near the maximum power (which varies from 8 to 16 A depending on the country).

Mode 2: Non-dedicated socket with cable-incorporated protection device

The vehicle is connected to the main power grid via household socket-outlets. Charging is done via a single-phase or three-phase network and installation of an earthing cable. A protection device is built into the cable. This solution is more expensive than Mode 1 due to the specificity of the cable.

Mode 3: Fixed, dedicated circuit-socket

The vehicle is connected directly to the electrical network via specific socket and plug and a dedicated circuit. A control and protection function is also installed permanently in the installation. This is the only charging mode that meets the applicable standards regulating electrical installations. It also allows load shedding so that electrical household appliances can be operated during vehicle charging or on the contrary optimise the electric vehicle charging time.

Mode 4: DC Connection

The electric vehicle is connected to the main power grid through an external charger. Control and protection functions and the vehicle charging cable are installed permanently in the installation.

Connection cases

There are three connection cases:

  • Case A is any charger connected to the mains (the mains supply cable is usually attached to the charger) usually associated with modes 1 or 2.
  • Case B is an on-board vehicle charger with a mains supply cable which can be detached from both the supply and the vehicle – usually mode 3.
  • Case C is a dedicated charging station with DC supply to the vehicle. The mains supply cable may be permanently attached to the charge-station such as in mode 4.