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This special guest post was contributed by By Chase Ballew, an EV owner and Portland State University student who was also featured in an article about electric car range anxiety on CNN. Keep up the great work and thanks for sharing Chase!

While a lot of attention has been given to electric vehicles themselves, a much more complex topic has been overlooked: electric vehicle charging. This article is intended to provide a detailed overview of the different types of Electric Vehicle Supply Equipment (EVSE), commonly referred to as charging stations. This includes a discussion of the different charging levels and how charging stations work, before delving into the subject of plugs and connectors. While this article is mostly in the American context, we’ll also take a look at charging internationally, and will conclude with a look at some of the more unusual or experimental schemes.

–Background–

In the late 1990’s, legislation in California known as the Zero Emissions Vehicle mandate (ZEV) forced automakers to produce electric vehicles. As part of this, automakers and the government spent millions installing electric vehicle charging stations in public places like grocery stores, shopping malls, public libraries, and park and rides, so drivers of electric vehicles could plug in. But there was a problem; each automaker used a different plug. A charging station for Ford’s Electric Ranger couldn’t recharge a Chevy S-10 EV. GM’s infamous EV1 could recharge at a station for Toyota’s RAV4-EV, but not the other way around. For consumers looking at buying a car costing upwards of forty-thousand dollars, a VHS/BetaMAX style format war was unacceptable. Automakers have gotten the message, and have agreed that all future electric vehicles, such as the upcoming Nissan Leaf or Chevy Volt, will use a new standardized plug, and the federal government, as part of the EV Project, is replacing many of the obsolete charging stations with the new standard, and installing thousands of new charging stations.

–Charging Levels–

Charging level refers to how much power is delivered to the vehicle. This is different from the charging station type, which refers to the plug used to connect the vehicle. There are currently three charging levels, although there may be more introduced in the future as technology changes. For reference, a vehicle like the Nissan Leaf with a 100-mile range would require 16-20 hours to recharge with level-1, 8 hours with level-2, and less than one-hour with level-3.

Level-1
Level-1 charging is the most basic and is done from a regular household electrical socket with 120volts at 15 or 20amps. Level-1 is common for recharging golf carts, low-speed Neighborhood Electric Vehicles (NEVs), and vehicles with small batteries. Plugging into a regular household electrical socket provides about 4 miles per hour of charge, which is considered much too slow for a full-size, highway-capable electric vehicle like the Nissan Leaf, which would require 16-20 hours to fully recharge, or the Tesla Roadster, which would require over 30 hours to fully recharge. For this reason, most highway-capable electric vehicles are designed to use level-2 charging, although with an adapter most can use level-1 in an emergency.

Level-2

For faster charging than can be accomplished with a regular household outlet, Level-2 charging uses a 208-240volt circuit, similar to that used to power a stove. However, the simple plug used to connect a stove would be unsafe outdoors in the rain, so the national electric code requires a special connector for level-2 charging which, when combined with required safety interlocks and cutouts, ensure the user can safely plug-in and recharge the vehicle in any weather condition. An selected overview of the national electric code’s requirements is in the section ‘How Charging Stations Work.’ Amperages for level-2 vary from 16 to 70, dependant on the building wiring, connector used, and the vehicle’s capabilities. Note that in North America, residential power is split phase resulting in 240volts, while commercial power is three phase resulting in 208volts. Because of this difference, drivers can typically recharge faster at home than at public places like shopping malls.

Level-3
Level-3 charging is now beginning to appear in North America, and is also referred as DC Fast-Charge, or DC Quick-Charge. Operating at up to 480voltsDC and 125amps, Level-3 will charge a vehicle like the Nissan Leaf to 80% in 28 minutes, with a full charge taking somewhat longer. Level-3 charging stations will be rare, in part because of their extreme cost; a public level-3 charger can cost over $100,000, compared to $3,000 for a public level-2 charging station. While Level-3 recharges a vehicle’s batteries quickly it will degrade the batteries if done repeatedly, and so is not intended to replace overnight charging at home, but rather to supplement it, facilitating longer journeys.

–How Charging Stations Work–

It is important to understand that the function of level 1 and 2 charging stations is only to provide an interface between the vehicle and the electrical grid. These charging stations do not actually charge the vehicle’s batteries; this is done via a battery charger built into the vehicle itself that converts the AC mains power to direct current of the appropriate voltage for the batteries. While the charging station provides an array of protections and interlocks to ensure safety, the fundamental function of the charging station is simply to supply AC mains power to the vehicle’s on-board charger. Level-3 is different, and is discussed in its own section below.

For level-1, moving power from the grid to the vehicle is quite simple. Since level-1 uses a regular household outlet, specifically the NEMA 5-15 or NEMA 5-20, many golf carts and NEVs are configured to simply use a regular extension cord to plug in the vehicle. Highway-capable EVs like the Nissan Leaf come with a special extension cord with a household plug on one end and the standardized J1772 EV connector on the other. For added safety these special cords also include over-current and ground-fault protection to supplement the protection included in the building wiring.

Level-2 charging is much more complicated. The high voltage used in level-2 charging makes it more hazardous, so Article 625 of the National Electric Code requires a large number of safety systems, which together make it effectively impossible for users to be electrocuted when plugging in, even in the rain. The level-2 charging station uses a connector (plug) unique to electric vehicles, to ensure drivers only use dedicated charging stations with the appropriate safety equipment. This unique connector and cord are permanently attached to the charging station, and have no power when not connected. Once the connector is securely latched to the vehicle inlet, the vehicle sends a pilot signal to the station, and only then is power supplied. For added safety, the connectors are designed so users cannot touch the metal contacts with their fingers, even though no electricity is present when not connected. Because drivers are sometimes forgetful, the vehicle is designed so it cannot drive away while plugged-in, and if it somehow does the charging station will safely shut off the power before the cable breaks away. Over-current and ground-fault protection are also required, as well as addition protection systems not listed here; for more information, refer to the National Electric Code, article 625, available online or from your local library.

–Connector Standards–

For safety, Electric Vehicle Supply Equipment (EVSE) must use a unique connector unable to power any other device, and while a standardized connector has now been agreed upon, there has been much variation in the past.

While there are several different designs of connector, they fall into one of two categories; conductive, which has metal-on-metal contact the same as any other plug you might find in your home, and inductive, which has no metal contacts and is essentially a form of wireless energy transfer using magnetic fields. Some automakers favored the inductive system, as it was impossible for drivers to electrocute themselves; the president of GM even demonstrated the inductive paddle system being used safely in a fish tank, but this safety came at great financial cost. As a result, other automakers favored the metal-on-metal conductive system, because the required interlocks and protection systems made it nearly as safe as the inductive for a fraction of the cost. Conductive charging was also more energy efficient; with inductive charging, as much as 20% of the energy was lost, compared to less than 2% for conductive systems.

Inductive Charging
Within the U.S. there have been two inductive charging systems, known as the Large Paddle Inductive (LPI) and the Small Paddle Inductive (SPI). At least one source notes an additional inductive paddle format, observed at the Walnut Creek BART station in Northern California, but I have been unable to find additional information. Further, there are other inductive charging schemes in development, discussed in the international section.

The Large Paddle Inductive (LPI) format, developed by MagnaCharge, was supported by General Motors in the 1990’s. The Large Paddle Inductive was replaced by the Small Paddle Inductive, which in the 1990’s was supported by Toyota, Nissan, and others. This is in part because it was smaller and so required less space on the vehicle, as well as being half the weight, making it easier for users to lift, but also because of the way the pilot signal worked, discussed below. Vehicles designed for large paddles (GM EV1, Chevy S-10 Electric, Nissan Altra EV) can use small paddles with the use of a plastic adapter that keeps the smaller paddle aligned in the large opening, but vehicles designed for small paddles (Toyota RAV4 EV, Nissan HyperMini) cannot use large paddles as they won’t physically fit in the inlet.

When the transition from large to small happened, the previously installed LPI units were supposed to be swapped out for SPIs, and 323 of them successfully were. However, midway through the transition the California Air Resources Board (CARB) decided to support only the conductive standard for public charging stations, terminating the upgrade process, so many LPIs remain. While the LPI standard is officially obsolete, the small paddle inductive remains the official standard for inductive vehicle charging as SAE J1773; however as CARB won’t support any inductive charging infrastructure automakers are no longer using inductive charging. For legacy support, inductive stations have continued to be installed and maintained in California by the non-profit Electric Automobile Association (EAA).

As discussed above, the electrical code requires that the charging station cord and connector be unpowered when not connected, and the vehicle sends a pilot signal to the charging station when connected. Conductive systems use metal contacts to send this signal, but with inductive charging systems there are no metal contacts. Instead, RF (radio frequency) communications were integrated into the Large Paddle Inductive system so the car can ‘talk’ to the charging station. This RF system was discovered to conflict with Japanese cell phones, so the Small Paddle Inductive stations used IR (infra-red) communications. Charging stations installed during the transition from LPI to SPI provided legacy support, having both RF and IR, with the intent of eventually phasing out the RF, but with the CARB ruling inductive charging was abandoned before that phase-out could happen, so all existing SPI charging stations support both. Neither RF nor IR communications are needed with conductive charging, where communications are through metal contacts on the connector, resulting in cost savings and improved reliability.

Conductive Charging

In the 1990’s conductive charging was done via a now obsolete rectangular connector developed by the Avcon Corporation, and supported by Ford, Honda, and others. This connector is referred to as the AVCON (uppercase for the connector, lowercase for the corporation) in much the same way as tissues are referred to as Kleenex or gelatin is referred to as Jell-O regardless of the maker, and in fact most public charging stations using the AVCON standard were manufactured by another company, Electric Vehicle Infrastructure. Colloquially, the AVCON connector is referred to as a “claw” to prevent confusion with the inductive “paddles.” The Society of Automotive Engineers standard for conductive charging is SAE J1772, and the AVCON connector is the 2001 revision, SAE J1772-2001. The AVCON is being replaced with a new connector, the J1772-2009 because it is needlessly bulky and complicated to use, the angle at which it must be inserted is awkward, and the maximum of 32amps is too low for today’s larger batteries (the number of amps determines the rate of charge).

The new SAE J1772-2009 replacing the AVCON is a round connector with an easy to use pistol grip, developed by Yazki. Eventually it will develop a popular name much as the AVCON did, but for now it is just known by the SAE number. All of the major automakers have agreed to use this new standard for their upcoming electric vehicles. The 2009 revision of the J1772 standard is capable of charging up to 70amps, much faster than the 32 amps for the AVCON, although most installations will likely be less than that. Unlike the two inductive standards, the two conductive standards are not backward-compatible, meaning cars that currently use the AVCON will not be able to use the new J1772-2009 without modifications to the vehicle. However, the new J1772 is intended to be forward compatible, so cars that use it now will be able to use future versions, which
in the future may also provide Level-3 DC charging and potentially an additional level of AC charging.

The new J1772-2009 format supports both level-1 and level-2 charging. This is an important consideration, as previous generations of electric cars only supported level-2, so if the batteries ran out away from a level-2 charging station, recharging from a 120v household socket (which in an emergency can be found just about everywhere) was exceedingly difficult and cumbersome. With inductive charging this required a “convenience charger” the size of a large toaster, but much heavier, that was stored in the trunk and had to be removed and plugged into the front of the car. (In the case of the RAV4-EV, this was intentionally inconvenient, as using it too often damaged the batteries.) Having the new J1772-2009 support both level-1
and level-2 charging natively greatly simplifies matters.

Level-3 Charging
Level-3 charging is also complicated. Also referred as DC Fast Charge, or Quick-Charge, Level-3 differs from 1 and 2 in that the battery charger is mounted off-board, and the connector plugs almost directly into the batteries. Because of the high voltages and amperages, the unit is large, the size of a refrigerator, and generates a lot of heat, making it impractical for on-board charging as is done with levels 1 and 2. Future revisions of the J1772 may support DC charging through the same connector in use today, but it is unknown if or when this will be developed as provisions for DC charging were removed in the 2010 revision. Further, because technological advancements will inevitably reduce the size of the charger and the heat buildup, level-3 chargers may one day be built into the vehicle much as level-1 and 2 chargers are today, and the J1772 could also support an additional level of AC charging to facilitate this.

A competing format, the CHAdeMO connector, was developed by Japanese automakers and the Tokyo Electric Power Company, and so is also known as the TEPCo connector. Some sources also refer to it as the JARI level-3, for the Japanese Automobile Research Institute. The Nissan Leaf and Mitsubishi i-Miev use the CHAdeMO standard, as did Japanese spec RAV4-EVs. America’s first public DC Quick-Charger using the CHAdeMO connector, was installed in Portland, Oregon at the Portland World Trade Center. A similar charger was installed in Vacaville, California several months before the one in Portland, but the one in Vacaville is not open to the public.

Whether the CHAdeMO or a future upgraded J1772 will prevail is as yet unknown; the CHAdeMO was first to the market, installed both on the ground and on vehicles, but the single connector inherent in the future J1772 has advantages, despite being years or decades in the future. Unfortunately, this sets the stage for yet another format war down the road. Further, this is not the first time level-3 has been developed. In the 90’s Aerovironment produced a level-3 charger called PosiCharge, once used with the Ford Ranger EV using a variant of the AVCON; PosiCharge is now used by industrial equipment like forklifts and airport ground equipment using a different connector. In 1998, GM and Southern California Edison installed a prototype quick-charger that used a modified LPI, but no production vehicles were ever made that could use it.

One final note on domestic charging standards; the Tesla Roadster currently uses its own charging standard, a round design similar to but larger than the J1772-2009. This connector was designed for 70amps, and when the new J1772-2009 was being designed Tesla insisted that it have the same capabilities. Tesla has said that it will upgrade the inlets on their vehicles to the new J1772 -2009 as those charging stations become more common, so this connector should be disappearing soon.

–International Charging–

One complication with charging internationally is that in much of the world level-1 does not exist; 120volt power is mostly unique to North America, Japan, and parts of South America. Elsewhere, (Europe, Africa, Australia, etc.) power in homes and businesses is 200-240volts single phase. (For more information on international power distribution, see: http://en.wikipedia.org/wiki/Mains_power_around_the_world). Because of this, in much of the world level-2 charging is done with the domestic plug; for example the JuicePoints being deployed around London use the 240v UK domestic plug with user-supplied 240volt extension cords, no special connector required.

Other vehicles have used various International Electrotechnical Commission (IEC) industrial plugs for charging, which are off-the-shelf and waterproof, but not specific to EVs and are quite bulky at higher amperages. The Mennekes connector, a new EV connector based on the IEC industrial plugs and compliant with IEC 62196, has been accepted as the standard EV connector in Europe. Physically, the Mennekes connector and the J1772 are not interchangeable; if the proper adapters were fabricated it may be possible to transfer power from the Mennekes to the J1772, but not the other way around. The Mennekes is designed for the 3 phase power common in many European countries, while the J1772 does not have enough pins to support 3 phase power.

There was also a UK version of the AVCON, but it was limited to 14amps, and like its American counterpart it is no longer in use.

–Experimental Charging Systems–

Nationally and internationally, there are experiments with new systems of charging. This is not meant to be a complete list, but should give a hint as to the diversity of ideas, yet through one means or another nearly all of them intended to eliminate the perceived hassle of manually plugging in the vehicle.

A number of systems are being developed to recharge parked cars with the use of plugs. Evatran is working on their “Plugless Power” system, which embeds inductive coils in the floor of the parking stall, but this suffers from low energy efficiency and high cost. Another company embeds a movable inductive coil in the parking block that automatically moves to align itself with a coil on the car’s front bumper; the closer alignment improves efficiency, but is still far less efficient than simply plugging in. The energy wasted by these inductive charging systems, multiplied across millions of electric cars, is a steep price to pay for the small added convenience. For convenience without wasted energy, Honda developed a system, now discontinued, that used knee-high robotic arms to plug in the vehicle.

Other systems intend to recharge vehicles without stopping. The Korea Advanced Institute of Science and Technology is field testing a system called OLEV that uses inductive coils embedded in the road to power and recharge vehicles at speed. In use in a parking lot shuttle at an amusement park, the OLEV system shows promise for transit and other fixed-route vehicles. If transit agencies were to install it for busses, automobiles could theoretically use it as well, possibly leading to system expansion. Unfortunately, the prototype is only 60% efficient, but researchers expect to improve that figure. In Lausanne, Switzerland, port vehicles carrying shipping containers use a similar concept, developed by TTS Port Equipment of Sweden. China has a fleet of busses that are powered by ultra-capacitors instead of batteries, and recharge from overhead wires located only at bus stops instead of along the entire route like a traditional trolleybus you might see in San Francisco or elsewhere.

Other examples go beyond traditional charging methods, like automated battery swap stations such as those promoted by Better Place, which replace dead batteries with fresh ones. Vanadium redox batteries utilize electrolyte refilling stations, literally refilling the battery as though it were a gas tank. However this is beyond the scope of this article.

–Conclusion–

Electric vehicle charging is a complex topic, but by now you should have an understanding of how standards have changed and evolved, how the different charging levels deliver different amounts of power, and how the national electric code regulates charging stations under the hood. Those charging stations have had many different types of connectors, both inductive and conductive, and while a new standard has been agreed upon for level-1 and 2, the potential exists for yet another format war over level-3 charging in the future. International charging is similarly complex, but the Mennekes connector is beginning to introduce standardization to Europe. There are many experimental systems looking to eliminate the hassle of plugging in altogether, but whether this can be done efficiently and cost effectively remains to be seen.

Authors note:
Please be aware, as this is a complex and constantly changing subject and I have no formal training or education in this field, it is entirely possible that I have overlooked something, made a mistake, or otherwise not been 100% accurate. Should you spot an error or omission, please feel free to contact me at ballew@pdx.edu or leave comments below.

The information here has been gleamed from a wide variety of sources. Some of the more memorable sources on the internet are listed below.

• http://www.madkatz.com/ev/chargestation.html
• http://www.tuer.co.uk/charge-connectors.htm
• http://en.wikipedia.org/wiki/Charging_station
• http://www.evchargernews.com/
• http://www.altfuels.org/events/otherafv/quikchrg.html
• http://www.evnut.com/charger.htm

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