#28814
Sir Humphrey
Strataguru

    Speaking as one who has been driving an EV for 9 years, I would say, if possible, that the best would be a relatively cheap, slow, standard outlet for each unit at its allocated space. Icing on the cake might be a single fast charger in one of the visitor spaces. 

    People who don’t have EVs tend to assume that you would want to charge like you do now with petrol. That is, that you go to a special place for refilling, that refilling is rapid, that you only refill when near empty.

    In practice, with an EV, it is more convenient to plug in for a top up whenever you are home. Home charging does not need to be rapid. If you are home for a few hours before going out again you get a useful top up even from an ordinary 10A power point even if you are not full before going out for another local trip. If you are plugged in overnight, you will be full in the morning and you don’t care whether you got to full at midnight or 3AM. 

    Ideally, single outlets in allocated spaces would be wired back to the meters for the individual units. That way, electricity consumption would appear on the units’ own meters automatically without any need to involve the OC. Unit owners would be free to choose time of use metering or any other deal offered by the retailer of their choice. The units could also fund the wiring as required as EV uptake proceeds. The OC just needs to make sure that the wiring meets standards and is done by a competent person in a consistent manner.  I would suggest the OC should not permit more than 15A outlets to avoid overloading the supply to the site. Also, to ensure that the last person is able to have the same quality of facility as the first person. 

    If it is not practical to run cabling from the unit meters to the allocated parking spaces, then the OC will have to meter what it supplies to individual unit and bill those units accordingly. 

    It is possible that the available supply will not cope with a carpark full of cars all charging at their maximum rates. Systems exist to manage this automatically. A standard EVSE (electric vehicle supply equipment) can ‘talk’ to the on-board charger and negotiate the charge rate. So, for example, a set of linked EVSEs might start out with (say) 15 cars plugged in attempting to charge from an 100A supply (a single typical domestic supply). The EVSEs will tell all the cars that they can only draw 6A each. Charging will proceed slowly. Some of the cars are likely to have only driven a short distance and will be full quite quickly even with this slow charging. After (say) 5 or 6 cars have dropped off, the EVSEs will tell the remaining cars they can now charge at 10A. Charging proceeds more rapidly, though still slow, and eventually a few more are full. The EVSEs tell the remaining cars they can charge at yet higher rates, while staying under the 100A max for the supply. Eventually there might be only a couple left and they are told they can charge at (say) 32A. One of the cars might be able to take 32A but another might max out at 15A anyway. Such systems can record the total kWhs sent to each outlet for billing purposes. 

    Further elaborations might be that the OC gets time of use metering so that charging off peak is cheaper. Those who want to charge at peak times can do so and might charge relatively quickly as others are avoiding the peak. They would pay a premium for the privilege. Those who don’t need the charge immediately would have their cars set to only ask for charging in off peak times and would save some money. 

    A tricky question for retrofitting is how to fund it when only a few people will have an EV at first. In my OC, I have worked out that we would probably have an interim arrangement whereby some ordinary 15A outlets are installed at the unit owners cost as a temporary measure for the first 3-4 units in each of our five parking areas. This would be within the spare capacities of our five existing electricity supply boxes.  A sub-meter on each of the lines to each of the 15A outlets would let the OC bill each unit for its consumption at a flat per kWh rate. Eventually, we would have to remove those outlets and instead install a comprehensive system of linked EVSEs as described above. 

    I don’t think people would want just a single or a few shared charge points in a visitor area. You want to plug in when you get home and let charging sort itself out. You don’t want to have to always charge at a rapid rate (not good for the battery) and you don’t want to have to go back to the carpark to move the car to let others charge and you don’t want to find you have been blocked from charging by other cars sitting in the charging spaces.