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Articles on Electric Vehicles

December 30, 2014
Paul Gipe

Electric Vehicle Charging Stations or EVSEs


Electric Vehicles (EVs) are different from the cars we’re accustomed to. They use electricity stored in the traction batteries to power the vehicle. They don’t use gasoline or diesel fuel. As a consequence, true EVs--those vehicles that rely solely on batteries without “range extenders”--can’t use the existing network of gasoline stations and gasoline pumps to “refuel”.

EVs need electricity to charge their batteries and that electricity must come from somewhere. That “somewhere” is the electric utility network or “grid” and a cable that connects the EV to the electrical grid—the EV’s umbilical cord.

EVSE

The connecting cable, the special plug that mates with a corresponding receptacle on the car, and the electronic sensors and the mechanical relay that makes the final connection between the car and the grid is collectively called Electric Vehicle Supply Equipment (EVSE).

Colloquially, the EVSE is known as a “charge station”. However, the EVSE is not the battery charger, which is located in the car itself. The EVSE merely connects the car’s battery charger to a source of electricity.

Small Tank & No “Gas Stations”

Most EVs can be described as typical cars except with an important difference. They have very small gas tanks. And there are no--or very few--“gas” stations. In Bakersfield, the oil capital of California, there are only two or three public charging stations and only one of those provides a quick charge.

Thus, you have to charge at home. To do so, you must install an EVSE--or charge station--so that you can plug in your EV and recharge its traction batteries.

Charging Levels: 1, 2, 3

The Nissan Leaf is shipped with a “trickle charge” or Level 1 EVSE. This connects or plugs into a conventional 120-volt electrical outlet common across North America. To recharge the Leaf’s 24 kWh bank of batteries at Level 1 takes 21 hours!

If you drive your Leaf part of every day, Level 1 just isn’t practical. It works. We’ve done it, but it isn’t practical. Level 1 trickle charging is a backup for when all else fails. It’s the emergency charge station you carry with you “just in case” you run out of juice.

For everyday EV use, owners will have a licensed electrician install a 240-volt or Level 2 EVSE. Level 2 will operate on a dedicated circuit similar to that for an electric dryer or—for even more power—an electric welder. Our Leaf will charge in 3.5 to 4 hours connected to a Level 2 charge station and this is typical for cars with this size traction battery.

Level 3 EVSEs charge at an even higher voltage and current than Level 2. The Leaf, and other Japanese cars using the CHAdeMO standard, charges at 480-volts DC. They can recharge their traction batteries to 80% of capacity within 30 minutes.

In contrast to the other charge stations, Level 3 EVSEs include the charger. They have a high-voltage connection to the utility and convert the utility’s AC to DC at the charge station and feed high-voltage DC directly to the EV’s batteries, bypassing he car’s onboard charger. As a result of including the inverter, and because a Level 3 LVSE require higher-rated components, Level 3 charge stations are very expensive—in the range of $10,000 to $20,000. Thus, they’re not suitable for charging at home.

Level 3 charge stations allow both intracity and intercity trips with today’s EVs and can be found as part of growing public charging networks. Most Nissan dealers, for example, have a Level 3 charge station using the CHAdeMO standard.

If you’re driving any distance at all in today’s EVs you need a network of quick charge stations. They allow you to make trips beyond one charge with a wait to recharge of enough time for a cup or tea (from which the term CHAdeMO is derived) or a cup of coffee.

We installed a Level 2 charger on our home.

Our ClipperCreek EVSE

There are a lot of EVSEs to choose from. When Nissan introduced the Leaf in 2011, it partnered with AeroVironment to install their EVSEs for Nissan customers. Since then, the market for EVSEs has ballooned. All the major electrical suppliers offer their in house versions. Prices are roughly comparable.

All EVSEs basically do the same thing. They sense when the connecter is firmly mated with the receptacle on the car. They talk to the car and find out how much current the car wants to draw. They determine the current carrying capacity of the circuit and how much current they can provide. Then they tell a relay to connect the car to the circuit. When the car has reached its capacity, it sends a signal to the EVSE and the EVSE then disconnects the circuit—it turns itself off.

With so many brands to choose from, we narrowed it down to those with a California connection: AeroVironment and ClipperCreek.

 

I’ve known or worked with people at AeroVironment for three decades. They’re down in the Pasadena area. It would have been a natural choice. Unfortunately, AeroVironment fumbled badly a few years ago when it introduced a small wind turbine designed for rooftop installation.

I work with wind energy. I write books about it. I’ve tested small wind turbines at my own test site. I am a vocal critic of rooftop wind turbines for a host of reasons, mostly because it’s a form of greenwashing. Rooftop wind turbines never work as promised—when they work at all. Most are tied off (so they won’t turn) soon after they’re installed.

AeroVironment aggressively marketed their turbine, relying heavily on the company’s long reputation in pioneering aerodynamics, flight, and innovation in human powered vehicles—remember the Gossamer Condor. When the inevitable rumors began circulating that their turbines were not performing well on a terminal at Boston’s Logan International Airport, AeroVironment began stonewalling. Like the many flaky rooftop wind turbine hustlers before and since, AeroVironment wouldn’t return calls and clammed up. Then they quietly rolled up the business and no more was heard from them on their wondrous new technology.

This episode left a sour taste and called into question the integrity of the business. AeroVironment was out.

Meanwhile, ClipperCreek, a small company in the foothills of the gold country was receiving high marks from the very well-informed denizens of the online forum www.mynissanleaf.com. ClipperCreek has been building charge stations since the pioneering days of EVs in California. They had a commendable track record and they’d make a commitment to making EVs a reality long before others started jumping on the EVSE bandwagon.

What cinched it for me was when I called them and I got a real person—in California. Better yet, they knew what they were talking about and we could talk shop. They answered my questions. There was no hesitation of the “why do you want to know that” suspicion I encounter far too frequently in my work.

I’d done my homework already, but we went through the models so I could see how they handle these inquiries. I settled for their 40-amp model. And they confirmed what I feared that because the unit would be mounted outdoors, I’d need an “outdoor-rated” model—naturally. That meant the unit would have to be hardwired and thus, a bit more expensive installation than otherwise.

When 40 Amps is not 40 Amps

A word about circuit ratings in amps. In North America, most local authorities incorporate the National Electrical Code (NEC) and its requirements when approving any electrical installation below 600 volts. The NEC exists to prevent electrical fires.

Circuits must be able to carry both a specified voltage and current without overheating or otherwise failing. One of the criteria is the amount of current in amps a circuit can carry briefly, say to start an air conditioner compressor motor, and what it can carry continuously.

The nameplate rating is what the circuit can carry briefly. A 40-amp circuit is designed to carry 40-amps briefly before tripping the circuit breaker.

However, the same circuit can’t carry the same current continuously without unacceptable heating up the conductors. To stay on the safe side, the continuous current rating must be less than the nameplate rating.

The NEC standard for continuous current is 80% of the instantaneous or nameplate rating of the circuit. Thus, a “40-amp” circuit is rated to carry only 32 amps continuously.

An EV is more like a toaster that’s on for four hours than it is a refrigerator that turns on its compressor motor then turns it off after a few minutes. So ClipperCreek's 40-amp EVSE is actually limited to 32 amps. This is slightly overkill for us. Our Nissan Leaf's on-board charger only draws 27.5 amps. But the 32 amps that are ultimately available are a bit of “future proofing” the EVSE should our next EV have a more powerful onboard charger than the 6.6 kW version on our Leaf. With the 40-amp EVSE we could go up to 7.7 kW (240 volts x 32 amps) without a new EVSE, new conductors, and a new circuit breaker.

ClipperCreek’s 40-amp EVSE comes with 23 feet of cable and a J1772 SAE connector for plugging into the appropriate port on the EV.

Substituting the Electricity Network for the Gasoline Network

We are still at the very early days of electric cars. We are just now building out the EV charging system. We forget how extensive and all pervasive the fossil-fuel network of refineries, pipelines, storage tanks, service stations have become. It’s enormous in size and complexity today, but it wasn’t always so. It took time, generations really, for it to reach the stage we see today.

Fortunately, EVs and their charging network are a leap ahead of where the early liquid fuel network was at the same stage of development. We already have an extensive electricity network that reaches nearly everywhere. This is equivalent to the pipelines, refineries, and fuel tankers for gasoline and diesel powered cars.

We only need to establish the actual charge stations for EVs. They’re coming. Too slowly for sure, but they’re coming nonetheless.

We may have several more public charge stations even here in Bakersfield soon. Imagine that.


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