Why Electric Vehicles Need Special Chargers
Why can't we just charge our cars with the normal power outlets?
Companies like Fortum Charge & Drive and Virta keep installing electric vehicle chargers wherever they can. Shopping centres have them. Tesla even offers their own chargers for any Tesla owner.
The chargers – or Electric Vehicle Supply Equipment, EVSEs, as they are more formally called – are big and bulky. They are seen as a prerequisite to electric vehicle adoption. The Finnish government even offers subsidies for condominiums to install them.
Special electricity?
It sounds like an EVSE is doing something really special with the electricity they give to the electric car, like monitor the battery state and temperature, and adjust voltages, but it turns out this is not the case for normal AC chargers. The EVSE only provides four core functions:
- User identification, most often via RFID tag
- Power usage and state reporting
- Safety features and power switching
- Current limiting to the vehicle (but it's still the same electricity)
The first two are even optional, if the charger is in your garage, the user management is handled with a 2000-year old invention: the garage door. You probably don't even need to know how much exactly is the car consuming or the car's app and IVI system can tell you that.
There is a big difference with the now-standard Type2 charging socket and the household Schuko socket. The Shuko has 3 contacts: protective earth, live and neutral. One neutral is always needed for transmission, live actually provides the power and PE is there for safety. In comparison, the Type2 socket has 2 more live wires for transferring power and there we have the first reason we use the Type2 socket for electromobility: more power. The household Schuko socket is only rated for 16 amperes and can take that for only 2 hours before catching fire or melting. This means about 30km of range for the typical EV. The Type2 socket on the other hand is rated for 63A in 3 phases, meaning almost 400km of range in the same time period. In practice almost no AC charger is this powerful, but at least the limiting factor is not the connector.
More power from electric charging outlet?
Industrial 3-phase power connectors
Photo by: Bahntech, under CC BY-SA3.0, editedNow, if you have welded, used industrial machines or gone camping, you may be familiar with the red 3-phase power socket, or it's little brother, the blue 2 phase one. Why could we not use one of these common and existing connectors? The IEC 60309 standard that describes them offers a variant going to 3*125A! Much more than the pesky 3*63A with the type2 connector.
The type2 connector actually offers two more pins than the red industrial connector, the Proximity Pilot and Control Pilot. The Proximity Pilot tells the charger when the plug is connected and disconnected, which allows it to engage the locking pin. Unlike the Industrial connectors, the Type2 socket cannot be removed when power is flowing, making it a lot safer.
Safety of electric charging outlets?
The Control Pilot works during the actual charging. It sends pulses to the car, telling it how much current it can take. The way electrical circuits normally work is, they take however much current they want, and the electrical grid provides. The limiting factor is circuit breakers, which should trip if something is drawing too much power for too long (if they didn't trip something might catch fire instead). In the case of a fully electric car, the car's charging circuit can take a lot of power, a lot more than a normal residential electrical system can provide, so somehow we need to tell it to calm down. This offers another benefit: the chargers can talk to each other, and adjust the total load to the electrical system in real time. If there's only one car charging, it gets the juice. If there are ten, they can be charged one at a time, or all together, but slowly.
So do you personally need a type2 charger? Only if you need a lot of power or you need to manage how to distribute the power to many cars safely.
Most cars come with a Schuko-Type2 charging cable, which only works in one phase, at 8A power, and provides the communication and safety features. This is perfectly OK, when your car is sitting at home for 8-16 hours per day and you have a robust enough electrical infrastructure. Condominium parking lots, offices, and shopping centres cannot do without a Type2 charger.
Visa Parviainen
A technologist with a passion for business. Visa has worked with Global-100 giants and startups alike to create software, hardware and services.
