EVs get boost from new SAE standard for dc fast charging

  • Image: US and Euro combo connector pix.jpg
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Image: REMA Combo - photo credit REMA.jpg

REMA is among the companies that produce J1772 equipment. Shown here is the Combo Connection System with its twin lower pins designed for dc fast charging.

By updating up its standard related to the charging of electric vehicles, SAE International is doing its part to help advance the EV market by allowing for much faster charging times—as little as 20 min.

Formally approved Oct. 2 after a vote of the relevant SAE committee members, revisions to SAE J1772 make it the only official dc charging standard worldwide, according to Gery Kissel. The General Motors Technical Specialist and Chair of the SAE J1772 Task Force told AEI that the lack of standardization to date has resulted in an unhealthy mix of charging systems—to ill effect for potential buyers of EVs and plug-in hybrids.

“If you don’t have appropriate standardization,” he explained, “you’re going to see continued fragmentation in the industry. That will lead to, I think, great confusion in the market and perhaps reduce customers’ appetite for this type of technology. Standardization really helps anchor things.”

Central to dc fast charging via revised J1772 is the so-called Combo Connector. The preceding version of the standard, adopted in 2010, spelled out the specifications for the J1772 Connector that is used for charging with ac power at comparatively low levels (ac Level 1 for 120-V charging and ac Level 2 for 240-V charging). The connector is in wide use today, being directly compatible with the Nissan Leaf, Chevrolet Volt, and Mitsubishi i.

Its specifications spelled out in the revised standard, the Combo Connector maintains all of the functionality of the previous version of the connector but includes two extra pins for the optional delivery of dc current for fast charging. The Combo Connector’s big payoff comes in the future as automakers can equip their upcoming EVs (defined here as battery-electric vehicles and plug-in hybrid electric vehicles) with a single receptacle that can accommodate the smaller previous-generation ac connector or the larger second-generation Combo Connector that can deliver ac or dc current at two different rates each.

Currently, the Leaf and the i have two vehicle receptacles—one for the previous-generation J1772 connector and one for the CHAdeMO connector developed in Japan.

Automakers will derive economies of scale related not only to the single-receptacle hardware, but also to the standardized digital communications technology behind it, according to Kissel. Similar economies of scale related to hardware and communications are expected “on the other side of the interface,” he said, referring to the Combo Connector and the charging stations in which they are used.

Europe is heading in the same basic direction, though it lags the U.S. in the pace of standardization and uses multiple IEC/ISO standards to produce the same end result as the single J1772, said Kissel. Insiders like him prefer to use the generic term “combo charging system” to get across the idea that in both regions vehicles will be equipped to accommodate charging with first- or second-generation connectors. Each region’s connectors differ in appearance from the other’s—mainly because Europe’s have two extra pins to accommodate the region’s three-phase electrical system (vs. one-phase in the U.S.)—but the communications and control behind the region-specific hardware is identical. The two regions worked together to agree on a combo charging system approach.

The word “connector” is somewhat ambiguous in that a connector (or plug) is only half of the physical system. The other half is the vehicle receptacle. Together they constitute a coupler, and that is the term used in the official title of the standard: “J1772: SAE Electric Vehicle and Plug-in Hybrid Electric Vehicle Conductive Charge Coupler.”

Kissel noted that the IEC/ISO standards for combo charging account for Japan’s CHAdeMO system as well as a unique charging system used in China. J1772 addresses neither of them.

Beyond dc fast charging, the newest J1772 revision enables advanced digital communications to be conducted over one of the pins within the legacy portion of the combo connector. The ultimate effect of this revision is larger bandwidth (a “fire hose, where before there was a straw,” Kissel said) to enable large data files to be downloaded quickly into the vehicle.

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