The Slow Process of EV Charging Standardization

By · June 12, 2012

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Two ports are currently in use on some plug-in vehicles such as the Nissan Leaf. The ports are known in the industry as the AC J1772 connector and the DC CHAdeMO connector.

We recently wrote about the imminent arrival of a combination EV charging connector that would enable charging AC or DC vehicles through a single charge port. When it arrives, this equipment, based on a standard that’s expected to be approved and generally available by August, will contrast with the two ports currently in use on some plug-in vehicles such as the Nissan Leaf. (The ports are known in the industry as the AC J1772 connector and the DC CHAdeMO connector.)

At industry events during the past year, I’ve been hearing a lot of talk about which DC charging connector will prevail, with several folks alleging that the “battle” between the Society of Automotive Engineers (SAE) and CHAdeMO (designed by the Tokyo Electric Power Company) is more about who gets to call the shots in the PEV market than about technical or business concerns. But, the issue is really about bad timing in the rush to get PEVs to market, engineers’ philosophical differences, and the slow process of standardization – and not something more nefarious. After more discussion about the DC charging evolution at the EVS26 conference, I went back and read the notes of my conversation a year ago with SAE standards participants to clarify the technical reasons why SAE didn’t adopt CHAdeMo.

In that conversation, I spoke with Rich Scholer (then at Ford and now at Chrysler), who was heading up the SAE working group on developing the messaging aspects of PEV standards, and Gery Kissel (at General Motors), who was heading up the working group on the connector aspects. They explained that the CHAdeMO connector has two additional terminals that allow controller area network (CAN) bus communications (used for communications inside vehicles) between vehicles and the off-board charging equipment. According to the CHAdeMO website, its engineers chose a redundant design with an analog signal transmission and a digital communication via CAN to ensure safe operation. (The SAE system similarly has both analog and digital communications.)

When it began developing a standard connector in 2007, which was long before any of this generation of PEVs had hit the market, the SAE decided it wanted a connector with few pins and that was as small as possible so it would be consumer friendly. When the SAE first began its standards work, the CHAdeMO specification was presented and considered for adoption, but the group ultimately preferred a single connector and chose to develop its own standard.

SAE began relying on power line carrier communications (PLC) when it began to work on an AC charging connector, and the group continued that philosophy with its DC charger development. PLC piggybacks digital communications information over the power line for communications with equipment off the vehicle. The new combo AC and DC connector will take the CAN messages and change them into PLC messages that are governed by the charger’s control pilot equipment.

In addition to these technical issues, the two groups had clearly differing philosophies on the urgency of providing a DC connector standard. Nissan, Mitsubishi, and other CHAdeMO backers wanted PEVs to launch with a fast charging DC option. At the time, SAE’s work was likely years away from completion. Since a CHAdeMO specification was available, they began shipping CHAdeMO-compatible vehicles in 2010 and were comfortable with a two-port solution.

Other automotive OEMs (largely in Germany and the United States) were not in as much rush to deliver vehicles or a DC charging standard. According to the SAE’s Kissel “the priority was always AC,” and that decision has led to the broad adoption of the J1772 connector.

More than 1300 CHAdeMO DC fast chargers have been installed globally, and Nissan and Renault are in the process of giving away 400 DC chargers in Europe so that CHAdeMO will become further entrenched in the region. Without referring to any specific technology, three European automotive groups (ACEA, CLEPA, and EURELECTRIC) said in late May that they “jointly agree on the need for a single harmonised plug system for the recharging of electric vehicles.”

The U.S. Department of Energy’s EV Project has also installed several CHAdeMO chargers. Any installed CHAdeMO charger would have to be upgraded to accommodate the new combo connector. New DC chargers featuring both CHAdeMO and the combined charger ports are expected out this fall.

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