Tesla Motors Club
Public charging infrastructure offers AC charging at 7 kW (J1772) and DC fast charging. If you have all day, J1772 can provide a useful amount of power. If you're in a hurry, DCFC (Superchargers and CCS) provide over 100 kW charge rates. But what about those occasions when you want more than J1772 but don't want to baby sit the car or rush back to the charger half way through a meal? Perhaps "Middle Charging" is the answer.
I suggest that EV users would benefit from an option of DC charging at 25 kW for locations where the driver will typically be occupied for over an hour before returning to the car. The obvious locations are shopping centers with food, movie theaters, fitness studios, grocery and retail shopping outlets. A 25 kW charger would probably put about 23 kWh into the battery after an hour. 90 minutes gives you 34.5 kWh and 2 hours yields 46 kWh. These are respectable amounts of charge and the lower charge rate doesn't heat up the battery like Supercharging. High power levels from DCFC get reduced as the battery state of charge reaches high levels but the 25 kW rate is already low so consistent charging speed will probably be obtained until SoC exceeds 80%.
Middle charging infrastructure is just a throttled back version of DCFC so existing electronics could be used to power multiple charging spaces. For example, DCFC electronics rated at 150 kW could provide power to 6 spots at 25 kW. Each location still requires the stand, charge control and metering function, and cable to connect with the vehicle.
I have suggested 25 kW but 30 kW (net 28 kW) might be better giving 60, 90 and 120 minute total charges of 28 kWh, 42 kWh and 56 kWh. A Model 3 SR+ can be charged over 90% in 2 hours with a 30 kW charger. From an infrastructure perspective, a single 150 kW DCFC electronics package can support 5 spaces at 30 kW.
If you have a charger at home or work then this might not be very interesting but if you happen to live in a condo, apartment or rented home without your own charger then the ability to integrate public charging into your normal routine might be very useful.
I suggest that EV users would benefit from an option of DC charging at 25 kW for locations where the driver will typically be occupied for over an hour before returning to the car. The obvious locations are shopping centers with food, movie theaters, fitness studios, grocery and retail shopping outlets. A 25 kW charger would probably put about 23 kWh into the battery after an hour. 90 minutes gives you 34.5 kWh and 2 hours yields 46 kWh. These are respectable amounts of charge and the lower charge rate doesn't heat up the battery like Supercharging. High power levels from DCFC get reduced as the battery state of charge reaches high levels but the 25 kW rate is already low so consistent charging speed will probably be obtained until SoC exceeds 80%.
Middle charging infrastructure is just a throttled back version of DCFC so existing electronics could be used to power multiple charging spaces. For example, DCFC electronics rated at 150 kW could provide power to 6 spots at 25 kW. Each location still requires the stand, charge control and metering function, and cable to connect with the vehicle.
I have suggested 25 kW but 30 kW (net 28 kW) might be better giving 60, 90 and 120 minute total charges of 28 kWh, 42 kWh and 56 kWh. A Model 3 SR+ can be charged over 90% in 2 hours with a 30 kW charger. From an infrastructure perspective, a single 150 kW DCFC electronics package can support 5 spaces at 30 kW.
If you have a charger at home or work then this might not be very interesting but if you happen to live in a condo, apartment or rented home without your own charger then the ability to integrate public charging into your normal routine might be very useful.