SAE Endorses Electric Vehicle Charging Standard

Back in September of last year, I wrote about an announcement that a group of auto manufacturers (Audi, BMW, Daimler, Ford, General Motors, Porsche and Volkswagen) had agreed on a standard set of connections and protocols for charging the batteries in electric vehicles [EVs].  Now, a post on the “Autopia” blog at Wired reports that the Society of Automotive Engineers [SAE] has officially adopted a version of this standard (called J1772 Revision B) for the United States and Europe.  The standard specifies the connectors and electrical interfaces to be used in public charging stations for electric and plug-in hybrid vehicles.

Using electricity instead of fossil fuels as a vehicle energy source has some significant attractions; but one problem that needs to be solved, in order for large-scale adoption of EVs to become reality, is the establishment of a charging infrastucture.  (We don’t think much about this with respect to our traditional, gasoline-powered cars, since the refueling infrastructure — gas stations — has been in place for many years.)  Having standards for the charging system is of obvious importance: imagine a world where a different kind of gas pump was required, depending on whether you drove a VW, or a Toyota, or a Ford.  It is, in a way, analogous to the question of whether we should drive on the right (as in the US), or on the left (as in the UK).  It isn’t obvious, at least to me, that either choice has any intrinsic or essential merit relative to the other; however, it is clearly quite useful for all of us to agree on a single choice.

Agreeing on a standard is also complicated by the number of factors to be taken into account.  It’s probably a fair assumption that most EV owners, most of the time, will use their standard domestic electricity supply (whatever that is, another variable) to recharge their car’s batteries.  That can be a slow process, though (measured in hours), using the standard US domestic supply at (nominally) 110-115 volts AC.  The standard also has to provide for an implementation that is safe to use in an uncontrolled environment (that is,  outdoors) in less-than-ideal conditions.

The new standard also makes some technical progress, while remaining backward-compatible with earlier versions of the J1772 standard.  In particular, it allows for high-voltage (~ 500 volts) direct current [DC] charging, which could reduce the time required for a full charge to 30 minutes or less.

This agreement on a standard is a good thing, but the picture is somewhat clouded, because some Japanese carmakers (particularly Mitsubishi and Nissan) had already adopted a Japanese standard called CHAdeMO to accommodate fast charging.

“We are disappointed that SAE has approved a fast-charging standard that will not accommodate more than 70 percent of the electric vehicles on U.S. roadways today,” Nissan America said in a statement. “At the time of launch, the Nissan Leaf was designed to comply with the CHAdeMO standard of quick charging, which was the only existing quick-charge standard certified at the time.”

Now, if this difference was only about two alternatives connectors and voltage levels and that sort of thing, as long as the standards are published, we should shortly expect to see adapters, to go from CHAdeMO to J1772-RevB, and vice versa.   I hope, though, that the auto makers will recognize that having a common, agreed, standard for recharging EVs is something they all should want.

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