EV charging standardized
The year 2010 is a landmark year for the Society of Automobile Engineers and electric vehicles.
This year, SAE has begun releasing important standards and guidelines to the international automotive manufacturing community regarding the electrification of the automobile power plant and drive train.
In mid-January, new recommended practices from the SAE's Hybrid Committee were approved and released.
The latest SAE documentation, called SAE J1772, defines a "smart" system for recharging plug-in, battery-powered electric vehicles. These specifications affect plug-in hybrid electric vehicles, such as the Chevrolet Volt, as well as pure battery-powered electric vehicles, such as the Tesla Motors Roadster and Nissan Leaf.
The documentation specifies the type of electric receptacle that must be mounted onto each manufacturer's vehicle, as well as wiring specifications, connector pin assignments and software communication protocols that will accommodate mating plugs from electric vehicle supply equipment.
As much as 16.8 kilowatts of single phase AC electrical power can be provided to an EV battery pack through this coupling system at two levels.
Level One is rated at 120 volts with a current transfer rate limited to a maximum of 16 amperes, while Level Two is rated at 240 volts with a current transfer rate up to 80 amperes.
The coupling connectors have five pins. Three of the wired pin connections conduct AC electricity from a recharging station with an "earth ground" for safety, just like any standard AC outlet in a home or garage. However, an additional pin connection communicates sensor information from the battery pack inside the vehicle to the recharging station. This "smart" two-way connection system enables communication between the recharging station and the vehicle battery pack.
SAE standards regulate every feature of the automobile, from its power rating in "horsepower" units to design practices for every possible component.
When the automotive industry faces an engineering problem, an SAE "working group" joins together to consider new designs and debate and specify solutions.
Hammering out new automotive specifications is not always a collegial process. Many competing automotive manufacturers would prefer to see their proprietary solutions be adopted by all other SAE members. Fortunately, any recommendations from the working group must go to the general membership for approval, much in the same way that a proposed bill in the U.S. Congress moves from a bipartisan committee to the general floor.
Stan Hanel has worked in the electronics industry for more than 30 years and is a long-time member of the Electric Auto Association and the Las Vegas Electric Vehicle Association. Hanel writes and edits for EAA's "Current Events" and LVEVA's "Watts Happening" newletters. Contact him at stanhanel@aol.com.
