EV charging isn't as simple as it seems - why your LEAF needs EVSE
Somewhere in the area of 100,000 people bought a plug-in electric car last year. Many of those buyers were quickly introduced to the often confusing world of home charging stations, a mixed bag of standards and compliance, and probably more than a little red tape and hoop jumping. These are the growing pains of the EV industry that fall mainly onto the consumers who are adopting these vehicles.
I noticed in the MyNissanLEAF.com forums that one new LEAF owner had a question about his EVSE installation and whether it had been done right, since the electrician involved had apparently not bothered to ask for permits from the city/county. A discussion ensued in which I realized that to someone on the outside looking in, a lot of this terminology might be confusing.
For example, what is "EVSE?" And why did this LEAF owner need an electrician or permits; don't charging stations just plug into the wall? Wait, someone said the Tesla charger is different? 30A has to be upgraded; huh?
Ya, it's a bit confusing to the uninitiated. For most drivers, just the imagined adjustment to remembering to plug into the outlet after parking at home is a big deal. Now you're telling them it's not even that easy. These are people used to just pulling up to a pump, grabbing the spigot that isn't green, choosing between 85 and 91, and pumping. It's an adjustment. So what do all these terms mean for the prospective EV owner who doesn't want to buy the cart and realize the horse doesn't exactly match the harness?
Home charging stations are installed according to the needs of the unit, which is chosen based on the electric car owner's vehicle needs and charging capabilities. No two EVs are likely to have the same needs, though most are similar. A new, but generally accepted standard called EVSE often means that the charger will require at least a 40 amp circuit to do "fast charging" (220-volt). This is not normally an issue, as many homes are capable of having a circuit that is powered by up to 50 amps, but most homes will not have a 40+ amp circuit already in place. The large, 3-prong "dryer plugs" for 220V we're used to seeing in our homes are actually 30A plugs and so are not suitable for many charging stations, though there are some that can use them by sacrificing charging speed.
To install a new charging station thus usually requires an electrician run new wiring on a dedicated circuit from the electrical panel to the installation location. This will need to be of high enough amperage to accommodate the charger being used. New installations require permits from the city or county for approval and inspection. All of this costs money, of course, How much depends on how difficult the job and where you are located. In California, it can be several thousand dollars.
A new electric vehicle plug-in standard for charging units called EVSE has arrived. It's been largely accepted by manufacturers of charging stations and has been in place for long enough that most of those being offered on the market today are probably compliant. EVSE stands for Electric Vehicle Supply Equipment, which is a control standard for the equipment itself. It doesn't necessarily need the car to be compliant with anything, though most are thanks to the SAE's J1772 protocols (the Model S does not use this standard, but is EVSE compliant). We'll get into J1772 in a moment.
To nutshell it, EVSE is a protocol that allows the charging unit to "think" for itself and to communicate with the car being charged. The charger knows how much current it can provide (via it's current electrical input capacity) at any given moment. Since every EV is slightly different, the amount that the car can accept may or may not be at that level. Until recently, car owners had to know their limits as well as what type of cord and plug they were using and set the charge accordingly. Manually. With EVSE, that's no longer the case.
The charger talks to the car, finds out its maximum input capacity, and then sends as much power as it can at or below that capacity. Sometimes the charger may not be able to draw sufficient load to power the car at maximum charging speed, other times the car may not be capable of accepting all that the charger can send. Either way, through EVSE, it balances out automatically.
This is a kind of breakthrough for plug-in vehicles, since it eliminates the need for a lot of user input and largely makes car charging plug and go.
J1772 is a Society of Automotive Engineers standard for electric vehicle plugs. You've seen these plugs on the Nissan LEAF, Chevrolet Volt, and others. They are the round plugs with the teardrop shape that allows the top to "lock" into the car's charge port. They have five plug wires in their round interface.
Looking at the plug with the "lock" at the top, the top two adjacent wires are power, the next one around clockwise is for communications (EVSE), the bottom one is the ground, and the one to the left is a safety control.