How To Choose EV Charging Point


    If you're reading this, it probably means that you already own an electric or hybrid vehicle or planning to do so and you're looking for some advice. But before going into the details of how to choose a correct charging point, let me explain what charging point/charging station/EVSE is and what's the main purpose for it. We will be talking here only about AC level 1 and level 2 charging points. We will not discuss about DC (Rapid chargers) at the moment.


    So what is AC charging point? Most people mistakenly thinks it's a device that charges your vehicle and do most of the hard work. It's not! It's an intelligent switch between your power supply and a vehicle installed charger. Yes, EV battery charger is installed inside your vehicle. And this in-car installed charger is doing the hard work of monitoring the battery and converting alternating current (AC) from your mains to direct current (DC) needed to charge your EV battery. So what is the purpose of having the external charging point, you might ask. Main purpose of charging point is to ensure safe connection and operation, providing highest protection to EV and user itself. That's why it's very important to chose a device that meets all charging equipment regulations (EN61851-1) and can provide as much protection as possible. What safety features should provide an advanced charging point? First of all it must ensure that power supply to plug or socket is provided only after charging point does a "handshake" with EV, and EV request a power supply to be activated. Also switching the power supply off as soon as charging has finished, fault developed or just before the plug is disconnected. This is done for number of reasons such as electrocution prevention, surge protection, electric arc prevention, fire hazard prevention and so on... Other safety features could be integrated RCD protection, existing Earth/Ground verification, stuck relay detection, overheat, overvoltage, undervoltage, surge protections. How many of these safety features are incorporated in the device is only up to manufacturer. Most important ones are must and usually present if device meets regulations. Be careful for devices with no CE, TUV markings. That means there is no guaranty it will do the job as it should do. If you spent your time doing bit of research about charging points, you probably seen some posts or even sale of DIY basic devices, that only switches power supply on after cable is connected to vehicle without any other functions or safety features. Such devices can't even provide the minimum protection required by current EV charging standards and should be avoided. Unfortunately a lot of people choose such devices because of simplicity or low costs and putting their property or even their lives at risk only to save few quid. We not saying these must be banned or people punished for using such a devices. In right hands of right person these can be used to develop something more advanced and used safely. But if you not familiar with electronics and have no interest in doing so, we would advise you to stay away from anything that is developed in-house.


    So after we got familiar with the term "charging point" and its main purpose we can start talking about other things you have to consider before getting one and what is advantages of charging point compared to EVSE cable supplied with the car.

    Two main benefits of permanently installed charging point is charging speed and safety. Other benefits could be integrated intelligent features such as timer, remote control, remote monitor and so on.


Charging speed

    Most of 3 pin charging cables supplied with vehicle are limited to 10A, which is equal to 2.3kWh (@230V). We will ignore the power looses for now to make calculations more clear and simple.

    Lets say vehicle is capable of charging at 6.6kW speed and we need to topup a 20kWh (130km @6.5km/kWh) of energy.

    To topup 20kwh of energy on a 7.2kW charging point (6.6kW as limited by car) it would take 3 hours and 2 minutes.
To topup 20kWh of energy on a cable provided with a vehicle it would take 8 hours and 42 minutes.

As you see it's almost 3 times faster to charge vehicle with maximum charging capacity of 6.6kW on 7.2kW rated charging point than using the standard cable that came with a vehicle. In reality this difference is even bigger, because there is energy wasted on cooling and in-car chargers efficiency drops at lower currents.


Safety

    When your charging point is wired permanently to consumer unit using correct size cabling there is less chances of fire risk because of no additional connections made in between charger and consumer unit. Loose or missing Earth/Ground fault developing chances are equal to zero if wiring is done properly. Also all permanent charging points must be installed on RCD protected circuit. Now think about using the charging cable supplied with a vehicle. Your vehicle will be constantly using 10A while charging. Knowing that some Europe domestic sockets are wired by 1.5mm2 cable and rated only up to 16A that gives a lot of chances of something to go wrong. Some people argue that all these wires are protected with 16A circuit breakers and there is no risk in exceeding the limit without triggering circuit breaker. They are wrong. To trip a 16A circuit breaker of curve B with current of 23A could take up to an hour. So if you got another 13A load on a same 16A circuit while charging your car with standard charging cable supplied, it would be 7A above rated cable current and it can take up to an hour for circuit breaker to be triggered. Doesn't sound good? Especially if your house wiring is older. Also there is still loads of old properties without RCD protected circuits, that leaves electrocution risk if cable gets damaged or gets wet. Not to mention loose or corroded connections inside the wall sockets or junction boxes. It is better, faster and safer to use permanently installed charging point, and use charging cable provided with a vehicle as a backup option. In case you still prefer to use charging cable supplied with a car or another portable charging controller, we strongly recommend at least to have separate power supply circuit installed which would be dedicated just for your EV charging.


    Ok, lets talk now about main things you have to consider before choosing a charging point. So main things you need to consider while choosing charging point for your home or office is: number of phases available at your property, plug type, voltage, maximum current of charging point, maximum current of power supply available and maximum charging capacity of the EV. Please bare in mind that we will be talking about terms only valid in Europe. We will not go into different region standards and differences as we only provide our service in EU mainland. So if you are from another region then Europe, please stop reading as the terms and explanations bellow will be incorrect for your region standards.



Earthing System

    Please read this very carefully as this is very important! In Europe most used earthing system is TN, which is compatible with all charging points made for EU market. But there is still plenty of very old properties and power grids that use TT and IT earthing systems, which will upset most of charging points equipped with advanced protection functions. So please check twice what earthing system is used at your property before making any purchase. Probably you will have to speak with qualified electrician or your electric power supply company to find out what system is used in your area or property. If you got TT or IT earthing system at your property please contact us first before making any purchase as these are not compatible with most the the products and power supply or device needs to be modified. We will advice of which product you should chose or what modifications need to be done. We will not accept returns or warranty if you purchased incompatible products without consulting with us first. So please complete your order only if you 100% sure your property earthing system is compatible with the sold product.

    The next picture is only an example of each earthing system. Please note that there are much more types of each system, but we will not get into the details of every different type and configuration.




Number of phases

    In Europe most of properties got single phase or three phase power supply. So if you decided you want three phase charging point, you have to check of how many phases are available at your property and if the Neutral is present at your main consumer unit. This is very important as some old properties in some countries (Norway, France, Belgium...) might still use very old three phase with no neutral system, which would only be compatible with specially designed/modified products. All charging points are either single phase or three phase. Some of three phase charging points can be used on a single phase if needed, but please always ask us about this before making a purchase.  What is the difference between three phase charging point and a single one? In theory same current rated three phase charging point can charge up to 3 times faster than single phase one. For example 32A rated single phase charging point can deliver up to 7.36kW of power, meanwhile same current rated three phase charging point can deliver up to 22kW of charging power. But don't get confused, as previously explained, it's not only up to charging point of how many phases your vehicle charger will use and what maximum charging power it can deliver to the battery. You have to do bit of research about your vehicle and what type of charger is installed in it. If you not sure where to start looking for this info, here is the link of some basic info about different make and model vehicles: ev-database. Chose your make and model and look under "Battery and Charging" for "Charge Power", also "Home and Destination Charging (0 -> 100%)".


Voltage

    Most of EU mainland power supply is either 230V single phase, or 400V(between phases) three phase. So all charging points sold in EU and caring CE mark will be compatible with your property power supply as long as correct phase type was chosen.


Plug type

    There is only two main EV charging plug standards on a market for AC charging. That's Type 1 (also known as J1442 or Yazaki) and Type 2 (also known as Mennekes). France also got their own Type 3 plug (known as Scame), but we will ignore this one as there is no mass produced EVs which needs this type of plug. Type 2 was officially accepted as EU standard for AC charging, so most of new EVs sold in Europe will come with type 2 charging socket fitted. Type 1 plug was only used for old vehicles made by Asian or American companies and is slowly disappearing from EU market. So we would strongly advise you to chose charging point with type 2 tethered cable or type 2 socket even if you got vehicle which needs Type 1 plug. Why? Because it's much wiser to invest in Type 1 to Type 2 adapter, than replace the charging point after you replace your old EV with a new one.


    What is the main difference between Type 1 and Type 2 plugs? First of all it is completely different looking plugs, physically not compatible with each other. The only similarity between them is that both standards uses same PWM signal on CP contacts which is used to communicate with a car in very simple way. We will talk about CP signals and communication bit later. Type 1 plug can only be used on a single phase charging equipment (in Europe). Meanwhile type 2 plug was designed to be used on a three phase charging equipment, but it still can be used on a single phase equipment without any issues. If you not sure of what type connector your vehicle is equipped with, please check these pictures to see the physical differences between these two types:

VS    

    Charging points equipped with its own cable is called tethered charging points. That means you don't need any additional cable or adapter to charge your vehicle as long as charging point got same type connector as your vehicle. If you got no EV extension cable to charge your vehicle or you don't want to use additional cables while using charging point you should chose tethered charging point. Another benefit of having tethered charging point is that cable fitted on it is always ratted to maximum available current of charging point. Also we found that plugs which comes with tethered charging points are always better quality than the ones you get on budget EV extension cables.


Maximum charging capacity of the EV

    This describes how fast your vehicle is capable to charge when provided with all the power needed to do this. All the hard work of charging EV from AC power supply is done by charger installed inside your vehicle. It's not the charging point that actually charges and monitors the batteries. It is in-car integrated charger. And same as all electrical equipment it's got its own limits. So before choosing the charging point you must find out of what is your EV maximum charging capacity.

    Lets have a quick example. Lets say we got Kia Optima Plug-in Hybrid and we are looking for optimal charging point for this vehicle. So by looking in to vehicles AC charging connector we can tell its Type 2 (Mennekes). And by looking into vehicles technical specifications we can see its Charge Power is only up to 3.3 kW on AC. So to be able to use full charge speed we only need 3.6kW (16A) charging point. We can buy and install a 7.2kW (32A) or even three phase 11kW (3x16A) charging point, but it will still be charging only at 3.3kW because in car charger is not capable to carry any more power. This doesn't mean you should only buy 3.6kW rated charging point. If the price difference is small between two different rated chargers and your power supply is capable to supply all the rated current to your charger we would recommend to go for higher rated one. Two reasons why; first: inside components will last longer as they are rated to carry higher currents, second: if you decide to change your vehicle with a new one, you probably wouldn't need to change a charging point if you chose more powerful one because it still might be powerful enough to keep you vehicles charging rate at maximum.


Charging point rated maximum power

    The more power charging equipment can carry, the faster it charges the vehicle. But again, it's not up to charging point if it will be charging at that rated maximum power. This is up to in-car built charger. Don't worry if you charging point is not rated to the maximum vehicles charging power capacity. In-car built charger will detect maximum rated power of charging point by charging points generated PWM signal and adjust the charging power accordingly. For example if you charging point is rated up to 3.6kW, but vehicles charger can charge at 7.2kW, vehicles charger will lower its charging power to charging point rated power.

    To simplify this we can use next formula:

 If Maximum charging capacity of the EV < Charging point rated maximum power then Maximum charging power = Maximum charging capacity of the EV;
If
Maximum charging capacity of the EV > Charging point rated maximum power then Maximum charging power = Charging point rated maximum power.


Power supply line rated current

    This describes how much current can be carried by your power supply line. This must be determined and calculated by certified electrician. For example if you been told that you can only have 32A power supply line for your charging point, that means you can only install up to 7.4kW rated charging point. To calculate maximum power by knowing the voltage and current you only need to multiply current by voltage. In this case 32A x 230V = 7360W or 7.36kW. NEVER install or use higher rated charging point than your power supply is rated for, this might cause a fire, injury or death.


How to calculate charging speed rate in km per hour of charging?

    To do so, first you need to find out how much kilometers you do by using 1kWh of energy. Most vehicles shows these parameters on the instrument cluster, you just need to look for average power consumption or average distance per 1kWh. Once you know this you need to do a bit off simple math.

    Lets say you charging at 3.7kW. So that means in ideal conditions you would add 3.7kW every single hour to your vehicles battery, in other words battery would gain 3.7kwh of energy. Lets say your average distance driven by using one kWh is 6.5km. So after you add 3.7kwh of energy to your battery you could drive 24.05km. This is your charging speed in kilometers per hour of charging. But don't forget this rate is only valid in system with 0% of energy loss. Most vehicle integrated chargers lose from 5% to 15% of energy while converting it from AC to DC, also some energy is consumed to cool the charging equipment and batteries. So you have to deduct these losses from your charging speed to get real life numbers.

Additional functions

    There are loads of other things you should consider before investing in charging equipment, such as need of remote control, remote monitor, timer or some kind of security lock. But we won't go into details about them as these are not critical things to consider and every person has different needs. If you need advise about such additional functions and what to look for, please feel free to contact us, we will be more than happy to answer your questions.