Engineers from BMW AG and General Motors recently passed a milestone in the adoption of the new Society of Automotive Engineers industry standard for DC Fast Charging. Teams from both companies worked jointly to ensure the conformity of DC “Combo” Fast Charge stations developed by various suppliers to the SAE standard by charging pre-production versions of the BMW i3 and the Chevrolet Spark EV.

This industry-coordinated early confirmation of DC Fast Charge hardware and software will accelerate efforts to roll out SAE Combo DC Fast Charge infrastructure in the coming months. Among the suppliers who participated in the testing were ABB, Aker Wade, Eaton and IES.

“Our goal with this cooperation was to ensure that DC fast charging stations be available to provide BMW i customers the premium fast charging experience in time for the arrival of the BMW i3s,” commented Cliff Fietzek Manager connected e-Mobility at BMW of North America, LLC. “We are pleased that we will meet our goal.”

“This unprecedented cooperation among OEMs and equipment suppliers demonstrates the maturity of this important technology that will help speed the adoption of electric vehicles around the world,” said Britta Gross, Director, Advanced Vehicle Commercialization Policy at General Motors.

Just as the majority of the world’s major automakers adopted the SAE’s 120V/240V AC connector standard to assure plug-in vehicles could access all charging infrastructure regardless of vehicle make or model, auto manufacturers (including BMW, General Motors, Ford Motor Company, Chrysler, Daimler, Volkswagen, Audi and Porsche) have committed to adopting the SAE combo fast charge connector, which assures standardization of the DC Fast Charge connectors.

This new combined AC and DC charging, or combo, connector provides added ease of use for DC Fast Charging, including a single charge port on the vehicle, and allows electricity to flow at a faster rate, making EVs more convenient to use for consumers who may not otherwise have convenient access overnight to charging at home. Using DC Fast Charging, EV owners could recharge their batteries up to 80 percent in less than 20 minutes.

“This successful testing is an important milestone that underscores our commitment to enable the next generation of electric vehicles, ” noted Cal Lankton, Director of ABB ‘s EV Charging Infrastructure for North America. “By offering a broad charging portfolio, we can fully support the needs of all EV drivers and infrastructure providers”.

The first vehicles to offer the new SAE Combo DC Fast Charge connector will be the BMW i3 and the Chevrolet Spark EV. DC Fast Charge is expected to be available when the BMW i3 launches in the US.


The physical couplers differ slightly between the U.S. and Europe, but the communications underneath are the same. (SAE International)
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