What does a EV charging point actually do?

I have bought a 2nd hand Nissan leaf and have been happily charging it slowly from a 13A socket (fed by solar panels) for 6 months using the "granny lead" that comes with the car.

Yesterday, when I turned it on, the READY and CHARGE light flashed about once per second, as did the lights on the dashboard, and there was a click each time from the unit. The manual does not list this combination as indicative of anything.

This lead me to wonder what the "charging unit" actually does, It lists its input and output as 250V ac so it clearly is not a transformer/ rectifier. If it is a protective relay measuring neutral earth voltage, then maybe the ON / OFF is caused by something happening to the voltage in the house?

I have not found any information on the internet as to what is inside these units.

  • I think you are referring to monitoring live neutral voltage to help detect open pen faults, in an open pen fault the neutral and earth connection will raise to the same voltage. I don't believe the type 2 granny chargers support this feature, due to this and risk of overheating the socket and supply circuit they are not recommended for regular use.

    Under voltage implies an open pen issue. But it's more common to have an over voltage issue with solar because the grid wasn't designed to deal with solar generation being fed back in, quite often this results in high supply voltages, above 253V. If this is the issue it's time to ask the DNO to reduce the supply voltage.

    Cutting in and out could also be because of overheating or maybe a poor connection on one of the control pins?

  • I bet the car takes days till its fully charged on a 13amp granny lead?

  • I bet the car takes days till its fully charged on a 13amp granny lead?

    Depends on how "empty" it was to start with - not may people run the battery completely flat before re-charging. Even then at say 2.4kW (10A) a 48kWh battery can't take much longer than 20h.

      - Andy.

  • Anyway the OP says he has been charging it for 6 months (!) Joking aside, for folk who do not use a vehicle hard every day of the week, then a 13A lead may well be more than enough, as an overnight charge will be tens of kVA, and even a 100kVA battery (sporty Tesla) will only need 30 hours  or so from dead flat to full.


  • It would be interesting to see the thermal effects on that plug and socket arrangement after regular 20 hour charging periods.

  • Some ordinary 13A are known to have problems. Ones marked EV on the back should be OK. Type 2 charger manufacturers seem to aware of the problem - some units incorporate temperature monitoring into the plug, others limit the current to something well below 13A (10A is common).

    Hopefully no-one's tried plugging two of them into a double socket...

       - Andy.

  • You said that electric car chargers are just long wires with plugs. They have lights that show if they are working and connected to the car.
    I don’t think so. Electric car chargers are devices that control how much electricity goes from the power source to the car battery. They have different features that make them better and safer than normal plugs.
    For example, some chargers can let you choose when to charge your car, depending on the price or the greenness of the electricity. Some chargers can start charging again by themselves if the power goes off. Some chargers can be used with a phone app, which can tell you how full your battery is, how much your charging costs, and where you can find other chargers.
    Electric car chargers also have safety features that protect you and your car from dangers. For example, some chargers can stop charging if the battery is full, too hot, or has a problem. Some chargers are also made to resist water, dust, or damage.
    By using a charger, you can also charge your car faster and easier than using a normal plug. Chargers have different power levels that affect how fast they charge. For example, a slow charger can take 8-10 hours to fill up an electric car, while a fast charger can take 3-4 hours. A very fast charger can take less than an hour.
    So electric car chargers are not just long wires with plugs. They are smart and safe devices that can make your electric car better. I hope this helps you understand them more.
    By “charger”, I mean the device that connects your electric car to the power source, at home or outside. It is also called a “charging station”, a “charger”, or an “EVSE” (electric vehicle supply equipment).

  • True, for the DC chargers, not for the AC ones that are the most common here - the EVSE contains a contactor that supplies mains to the car when certain conditions are met - including have you paid if it is a public one.

    The actual charger functions as you describe them are performed inside the car - which is logical, as only the car knows the voltage, amp hour capacity and temperature of its own battery. The EVSE tells the car it is a 3kW point or a 22kW point or whatever, and it is up to the charger in the car to make sure it draws no more than that. The EVSE may contain the equivalent of a phone with no handset to do the data connection for payment.


  • By “charger”, I mean the device that connects your electric car to the power source, at home or outside. It is also called a “charging station”, a “charger”, or an “EVSE” (electric vehicle supply equipment).

    The OP referred to a "granny lead", which seems to be something different.

  • The OP referred to a "granny lead", which seems to be something different.

    Granny leads are "mode 2" EVSE. Ones on the wall are "mode 3" (at least the domestic a.c. types). Functionally they are similar - the box in the lead of a mode 2 setup providing at least the basic functions of a mode 3 setup - i.e. communicating with the vehicle over the CP and PP wires (according to SAE J1772 and  IEC 61851-1/IEC TS 62763) to establish things like the that vehicle is connected (no exposed contacts), earth continuity (at least between vehicle and EVSE), available power (limited by both the supply equipment and the lead) and so on, and then only closing contacts to provide mains power once everything is satisfactory. Most provide at least the equivalent of 30mA RCD protection as well.

    Mode 3 units often provide many additional facilities - e.g. open PEN protection, metering, and/or internet connectivity - but in principle at least granny lead boxes could do that if they wanted.

    Simple leads would be "mode 1" - but these have pretty much been consigned to history already.

       - Andy.