Charging Standards musings

j1772 combo

So, being only about 6 months behind the times, the SAE released their combo plug standard about a week before Daytona happened.  With the Japanese CHAdeMO standard gaining popularity with the, Tesla doing their own thing and the J1772 AC charging stations looking inadequate in comparison, people were having a hard time understanding why the SAE was being so stuborn as to insist they needed their won standard.  Chelsea Sexton took a shot at the SAE (and everyone else kind of) in a piece for one of the major tech sites.  It looked like the SAE was just being silly arrogant Americans standing in the way of progress.  But it actually seems they really did have a better idea.

Before I go to deep lets review the differences between AC and DC charging.  AC chargers are actually nothing but fancy electrical sockets and rely on on-board chargers.  the problem with on-board chargers are that they are small.  Most Leafs only come with 3.kW chargers, only now to have a 6kw chargers as on option for the new cars.  An Empluse has a 3kW charger, and the Zeros are up to almost 2kW.  The Ford Focus electric was supposed to have come with a 6kW charger from last I knew, and the Tesla come with a 10kW and you have the option adding a second for 20kW on onboard charging power.  Most J1772 charging stations are good for 9kW, and the beefier ones even more.  It’s a bit of a waste really, especially when pretty much all of the batteries in EVs now a days can take up to a 1C charge.  In other words if you could put a 9kW charge on an Empulse you could charge it in an hour at just about every J1772 station out there.  But that charger would be HUGE, and there’s just no room.  The AC chargering stations are handy, and with a car as big as a Tesla, a minimum.  The on-board chargers will not get smaller, so what do we do?

Well we go DC charging.  This is, simply put, a big ass charger in the station, making it an actual charging station.  Examples are the CHAdeMO stations, and Tesla’s Superchargers.  These talk to your EV and bypass the onboard charger and feed the amount of DC power your BMS asks for.  Now you can charge from empty in almost an hour.  The issue is both the Tesla and CHAdeMO systems have their own plugs, with the Tesla coming with adapters, and in the case of the Leaf two different plugs.  Also, I believe the Tesla chargers have a higher max power capability (120kW) making them a bit future proofed.  Can you fit both J1772 and CHAdeMO sockets on your Zero so you can take advantage of both?  I don’t know, but it seems doubtful, expensive, and ugly.  What about DC fast charging for your Empulse?

Well this seems to be where the SAE actually had an idea worth making us wait for, a combo plug.  With this plug you can get DC fast charging at compatible charging stations (that have yet to really deploy anywhere), and you can use all of the old J1772 AC charging stations that are already out there.  Best of both worlds and much more convenient.  As far as your Empulse goes, we’ll have to pray Brammo comes up with an upgrade kit, but that seems a bit complicated.  However, if they come out with a new bike and it has the combo plug you will be able to use the old charging stations while waiting for the new DC stations start getting put up.  Zero, on the other hand, with their design can simply come out with a new plug that mounts to the bike and I assume a firmware upgrade and you’re off.  One socket to rule them all.  And if you have a ton of CHAdeMO stations in your area they still have the CHAdeMO sockets.  But that is all hopeful wishes as we wait for manufactures to make up their mind if they are going to buy into it.

Short of the long, the SAE has come up with a standard that allows you continue to use the AC chargers that are already out there while being able take advantage of DC fast charging as it continues to come out.  I like it.


SAE International Releases New Fast-Charging Combo Coupler Standard (SAE J1772) for Plug-In Electric and Electric Vehicles

WARRENDALE, Pa., Oct. 15, 2012 – SAE International’s much-anticipated technical standard for plug-in hybrid electric vehicle (PHEV) and electric vehicles (EV) has been approved and published.

Developed in a consensus environment by more than 190 global experts representing automotive, charging equipment, utilities industries and national labs, “J1772™: SAE Electric Vehicle and Plug in Hybrid Electric Vehicle Conductive Charge Coupler” enable charging time to be reduced from as long as eight hours to as short as 20 minutes.

“This new technical standard is a real game-changer,” Andrew Smart, Director of Industry Relations and Business Development for SAE International, said. “It reflects the advancements in technology within PHEV and EV engineering and we are pleased to represent the collaborative efforts within industry that made it possible.”

The standard represents the future of charging technology and smart grid interaction, while addressing the needs of today. Such needs include reduced times at public charging stations, enabling consumers to travel greater distances in their PHEV’s and EV’s.

“This new standard reflects the many hours that top industry experts from around the world worked to achieve the best charging solution – a solution that helps vehicle electrification technology move forward.” Gery Kissel, Engineering Specialist, Global Battery Systems, GM, and SAE J1772™ Task Force Chairman, said. “We now can offer users of this technology various charging options in one combined design.”

The original version of J1772™ defined AC Level 1 and AC Level 2 charge levels and specified a conductive charge coupler and electrical interfaces for AC Level 1 and AC Level 2 charging. The new revision incorporates DC charging where DC Level 1 and DC Level 2 charge levels, charge coupler and electrical interfaces are defined. The standard was developed in cooperation with the European automotive experts who also adopted and endorsed a combo strategy in their approach.

Click here to see the J1772™ SAE Charging Configurations and Ratings Terminology.

“J1772™: SAE Electric Vehicle and Plug in Hybrid Electric Vehicle Conductive Charge Couple” was developed and issued by SAE International’s J1772 Task Force. For more information, visit; call 1-724-772-8522 or email

SAE International is a global association of more than 133,000 engineers and related technical experts in the aerospace, automotive and commercial-vehicle industries. SAE International’s core competencies are life-long learning and voluntary consensus standards development. SAE International’s charitable arm is the SAE Foundation, which supports many programs, including A World In Motion® and the Collegiate Design Series™.

9 thoughts on “Charging Standards musings

  1. The best AC chargers take up less volume than you might think. The Empulse has a 3.5 kW AC charger that fits in less than half the space of a shoebox (3″ x 7″ x 10″). Packaging all the various box-shaped bits on an electric bike is no easy task – motor controller, battery boxes, chargers – but I don’t think it’s an impossible job, particularly if you start with that as a design constraint.

    I’d love to see a touring model of the Empulse that fit a pair of the Eltek chargers onboard. 7kW of AC charging should max out most publicly-accessible J1772 EVSE, which provide 30A @ 240V AC (~7.2 kW).

    Yes, you can fit both a J1772 inlet and a CHAdeMO inlet on a 2013 Zero.

    SAE combo does have an advantage in that the combined inlet size is somewhat smaller .. and *possibly* less expensive. It might even be a compelling advantage if you ignore the install base of CHAdeMO chargers and compatible vehicles that have been shipping for 2-3 years, and the years of fragmented charging standards to come.

  2. Thanks for the tip on the Zeros! Why are they not marketing that?

    Nothing wrong with CHAdeMO, but there are way more J1772 and they are cheaper. So small business could put a J1772 for little money, people can put then in the garages/on the side of their house, etc. I feel the new combo simply offers better convince and compatibility with an existing charger network in a more efficient use of space.

    I don’t blame Tesla for what they did one bit. I say good on ’em. I don’t think the charging thing will be too bad in the future. The SAE has a new standard that works with their old standard, well in one direction any way, CHAdeMO works and NIssan Leaf owners pay $7/hour in Chicago while Tesla owners get free fuel for life while . Europe has their own thing going, like they usually do.

    1. Probably because Zero’s support for J1772 is in name only, as a factory-stock Zero charges no faster from J1772 than it does from level 1 charging. I had hoped the Empulse would shame them into fixing that, but it seems that’ll have to wait at least until 2014.

      J1772 combo certainly requires less space and is perhaps less costly than J1772 AC + CHAdeMO, but it’s absolutely not more compatible. J1772 combo plugs have a “key” that physically obstructs the AC-side of a combo plug from being inserted into existing J1772 AC-only inlet .. and of course J1772 AC plugs work fine with either J1772 combo inlets or CHAdeMO + J1772 AC inlet pairs. I’m convinced this is by design – I don’t think J1772 combo EVSE are ever intended to deliver AC power over the AC pins.

      So bottom line, today if you want to service every EV sold in the US in the past decade, you need to support two charging standards (J1772 AC + CHAdeMO, not counting Tesla’s proprietary plugs). In a year you’ll need to support three, though many quick-charging companies are starting to support both J1772 combo and CHAdeMO with a single unit. That’s not a compatibility win in any sense.

    1. It’s not totally useless. New vehicles using a combo inlet can accept either existing AC plugs or new DC plugs. Existing vehicles using AC inlets can only accept existing AC plugs. So the existing J1772 AC infrastructure is not useless, it will still be very useful for longer charging intervals at work, movie theaters, sit-down restaurants, etc.

      My major problem with the standard is that it is so late and brings so little to the table. CHAdeMO has a 4 year headstart, though really only the last two years have seen significant EV / EVSE adoption. It’s a small improvement over CHAdeMO in that the inlets are smaller (and perhaps less expensive); but the power delivery levels are the same, vehicles still need to run five large-gauge conductors back to the battery/charger. Nice features like V2H, V2G are possible with the CHAdeMO connector too.

      Though the inlet assemblies are smaller than CHAdeMO + J1772 AC, the plug size is basically the same as CHAdeMO.

      Perhaps GM / Ford / BMW can pull a Tesla and stand up an EVSE infrastructure overnight. CHAdeMO is not very well established here in the US; I’ve estimated previously that $50-100M would roll out quick charging infrastructure along the 16000 miles of US interstate – 1 station every 20-30 miles.

      Estonia just rolled out a national CHAdeMO charging network.

      Somewhat unfortunate, as the EC just announced they’re adopting the Mennekes “Combo 2” quick charge standard. The standard Mennekes Type 2 plug can support up to 43 kW charging, either AC (single phase / 3 phase) or DC. It’s only beyond 43 kW that the combo plug is needed.

      The combo inlet should use a similar or identical vehicle cutout as SAE combo, just with a different inlet (and perhaps communication scheme).

      Whole situation is a mess. Imagine if there were different national standards for USB. : \

      1. Well I have one word for you, Firewire. 😉

        With almost every country have a different home plug design having 4 really doesn’t seem so bad. And if the European standard has a kW limit the new J1772 will probably take over as the packs get bigger. It’ll just take time.

        But I had thought you meant a J1772 AC plug wouldn’t work with the combo socket.

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