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SAE J1772 DC (Combo) Connector Adapter for Model S

Discussion in 'Model S: Battery & Charging' started by stopcrazypp, May 3, 2013.

  1. stopcrazypp

    stopcrazypp Well-Known Member

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    Since there's so much discussion on the CHAdeMO adapter, I decided to post a new thread about a possible SAE J1772 DC (Combo) adapter for the Model S.

    First thing to point out is what the socket and connector looks like:
    SAEcouplerDC.jpg
    The top two are the socket and connector for J1772 DC.
    The bottom two are the socket and connector for J1772 AC.
    The bottom right J1772 AC connector can plug into the top left J1772 DC socket
    The top left J1772 DC connector can NOT plug into the bottom left J1772 AC socket because of the plastic slot pointed out by the red arrows.
    This extra plastic slot is also why the existing J1772 to Model S adapter will not directly work with the new J1772 DC connector.

    Next thing to understand is that there are two DC modes:
    DC Level 1 - uses only the top J1772 AC half of the socket and provides up to [email protected] = 40kW of power
    DC Level 2 - uses the bottom two extra large DC pins and provides up to [email protected] = 100kW of power

    A recent presentation by the SAE confirms a Supercharger to SAE DC Level 1 adapter can be made for less than $100! It'll basically be exactly the same as the current J1772 adapter except modifying the plastic slot previously mentioned.
    attachment.php?attachmentid=21414&d=1367637725.jpg
    http://www.sae.org/events/gim/presen...rds_status.pdf

    Making an SAE DC Level 2 adapter will be a bigger challenge since there needs to be a connection to the two large DC pins on the bottom from the two large pins in the top of the Model S connector.
     
  2. pilotSteve

    pilotSteve Member

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    DC Level 1 - uses only the top J1772 AC half of the socket and provides up to [email protected] = 40kW of power
    DC Level 2 - uses the bottom two extra large DC pins and provides up to [email protected] = 100kW of power

    A recent presentation by the SAE confirms a Supercharger to SAE DC Level 1 adapter can be made for less than $100! It'll basically be exactly the same as the current J1772 adapter except modifying the plastic slot previously mentioned.


    But..... can an adapter also be made to allow Model-S charging at 40kW DC from SAE/ChaDeMo (Level 2 DC EVSE) that are quite widely installed in Oregon and Washington. Is this correct?

    If so this would be a great interim step for those of us with accesses to these DC chargers. I would happily pay $100-300 for such an adapter.
     
  3. highfalutintodd

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    There are a few giant threads discussing this. The most recent can be found here:

    CHAdeMO adapter frustration
     
  4. RDoc

    RDoc S85D

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    I didn't think that the simple J1772 plug could do DC charging at all. Everything I've read says it is AC only. It was my impression that DC levels 1 and 2 (and 3?) were only available in the J1772 combo plug and were done completely through the bottom two large pins. Could you provide a link to the description of how the Level 1 DC charging on the upper pins works?
     
  5. stopcrazypp

    stopcrazypp Well-Known Member

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    Like highfalutintodd says there are plenty of other threads on CHADeMO, which is an entirely different issue:
    http://www.teslamotorsclub.com/showthread.php/7107-Likelihood-of-a-CHAdeMO-adapter-for-the-Model-S
    According to most people (including Ingineer who has the expertise to make one), a CHADeMO adapter will cost over $1000, probably closer to $2000. This is because the CHADeMO connector is quite expensive and you also need electronics in between to translate. CHADeMO uses a CAN bus to communicate, with 10 pins in total. J1772 and Model S uses pilot signals and PLC, with 5 pins (7-8 pins for J1772 DC).

    The SAE DC adapter being discussed here is simply a pin-to-pin adapter to adapt two physically different connectors.

    A typical EV with a J1772 AC socket can not do DC charging via the top smaller AC pins at all (even if you made an adapter) because those pins will be directly connected to the onboard charger and will have no possible direct path to the battery.

    The Model S is different since it uses the same two power pins for both AC and DC (it already has contactors to switch between the two). I don't know however if any future Combo connector cars will also have this design.

    As for how I know level 1 DC can be done on the upper pins (something I didn't expect until after I seen the slide I posted):

    First clue is the rating, the current limit of J1772 DC Level 1 is 80A, exactly the same as J1772 AC Level 2, which suggests they are going through the same AC pins:
    http://www.sae.org/smartgrid/chargingspeeds.pdf

    Second clue is the slide I posted in the first post says "Level 1 DC Combo 40kW/43mm, <$100". J1772 43mm refers to the J1772 AC connector (it's 43mm in diameter). J1772 DC is 60-70mm.

    I don't have a copy of the spec (I probably should purchase one), but I did post a presentation that showed J1772 DC only needs 5 pins to do DC charging.
    attachment.php?attachmentid=3878&d=1326586231.jpg
    http://www.teslamotorsclub.com/showthread.php/7107-Likelihood-of-a-CHAdeMO-adapter-for-the-Model-S/page10?p=104399&viewfull=1#post104399

    If you look at the J1772 AC connector: Pin 1 & 2 are the AC power pins, Pin 3 is the chassis ground, pin 4 is pilot, pin 5 is proximity. The extra pins added by J1772 DC are Pin 6 & 7 (the two large DC power pins), Pin 8 is an extra chassis ground pin. As long as SAE DC has the DC charger be able to switch between Pins 6&7 and Pins 1&2 for power (depending on level 1 DC or level 2 DC), it's possible to DC charge using only the top half of the J1772 DC connector.
    https://code.google.com/p/open-evse/wiki/J1772Basics
     
  6. arg

    arg Member

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    These figures make the common mistake of multiplying max voltage by max current to give power. That's OK for AC charging where the voltage is constant, but always wrong for DC charging where the charger voltage has to follow the battery voltage. So in practice you never in fact reach the full rated voltage (depending on the car's configuration for how close you get), and for all cars the voltage will be lower at the beginning of the charge; then as you approach max voltage the current will be limited by the batteries rather than the charger/connector so that even if you get close to max rated voltage you will never be taking max current at that point.

    Looking at this http://www.teslamotorsclub.com/showthread.php/12078-Typical-Supercharging-rate?p=262066&viewfull=1#post262066 graph of Model S (super-)charging, the best you would get out of an 80A-limited DC charger is at about 85% state of charge: here the battery is at 400V and the current is 80A, so 32kW. Above that point, the current has to be reduced to protect the batteries and so the power delivered by the charger declines (and this area isn't of great interest as it's the Range Charge zone). Below that point (ie. most of the time), the battery voltage is lower and so the power delivered correspondingly less. With an almost empty battery, the voltage is about 360V, so the power only 29kW.

    Hence the average power through a normal charging cycle with such a charger connected to a Model S through the 80A-limited connector would be in the region 30-31kW.

    On the other hand, with the full "DC-level2" plug delivering 200A, it will be exactly the same as a Supercharger for anything above 50% state of charge (Supercharger doesn't exceed 200A here): about 74kW at the cross-over point. At the beginning of the charge, Supercharger is potentially delivering up to 90kW (though if that graph is typical, it doesn't always reach that level), while the SAE plug is limited to 72kW.

    Tesla may continue to fiddle with the rules for maximum current (as they appear to have done at least once since the first software release that supported Supercharging), but the battery voltage isn't going to change, so an "SAE DC-level2" charger is always going to be limited to 72-74kW while charging a Model S (and even if you built a car with a battery pack optimized for the SAE charger's 500V max output, it's still going to be more like 85kW practical maximum than the 100kW claimed).

    [This miscalculation is often seen in discussion of CHAdeMO charging too]
     
  7. RDoc

    RDoc S85D

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    I think we really need to see the actual SAE spec rather than trying to guess based on fragmentary power point slides.
     
  8. arg

    arg Member

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    You can get one from SAE here: http://standards.sae.org/j1772_201210/

    Cost is $68.

    I have a copy - it confirms the points earlier in this thread - max 80A DC through the contacts common to the AC connector, 200A through the extra DC pins. It also says that pins 1,2 (the AC/DC-lev1 pins) are not present in the level 2 connector (this doesn't affect mechanical compatibility, but does mean that they have excluded the possibility of using both sets of pins in parallel).
     
  9. qwk

    qwk Model S P2681

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    While technically possible, I really doubt that the AC part of the J1772 connector would be able to handle much DC charging @40kw. The bottom pins are there for a reason, and I suspect that those will be used for ALL level 3 charging. The Tesla TS2 connector is a totally different animal in terms of quality(silver plated connections), and very beefy. Not so with the J1772 AC connector.
     
  10. gregincal

    gregincal Active Member

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    And I don't necessarily see the utility. Yes it would make for a smaller and somewhat cheaper Model S adaptor, but at the cost of much reduced charging rate. Routing the bottom pins from the combo plug into the Tesla pins seems pretty easy even if it makes for a bulkier adaptor, since the top pins won't be used. Having an adaptor that handled both would be considerably more complicated and expensive.
     
  11. arg

    arg Member

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    Well, the spec only calls for about 30kW in typical use, and that is putting exactly the same stress on those pins as the 80A AC case (eg. Model S with twin chargers charging from 80A J1772 EVSE with the adapter). So if there is really a requirement for 30kW charging, then this is a valid way of doing it.

    However, the way the standard is written currently leaves a bit of an interoperability nightmare. It is possible for a car with the larger level-2 compatible connector to also support level 1 DC, that isn't mandated (at least to my reading). If it had been mandated it would have been straightforward: the car would support level 1 and level 2, and then when building the EVSE if it's under 80A (~30kW) you fit the smaller connector; over 80A you fit the bigger connector. However, the way it is now there can be cars that support DC level 2 (the other pins might be present but only support AC), so if you build an EVSE with the smaller connector it can't charge those cars.

    Fortunately in the Tesla case it all ends up on the same pins anyhow, so the existing J1172 adaptor will also work fine for J1172-DC-level1 if any ever exist, and a new adapter can be made for J1772 DC level 2.

    It might have been convenient to build an EVSE with the smaller connector and support both 30kW DC and 20kW AC, but that doesn't work conveniently either: the EVSE can't signal via the traditional control pilot that it offers AC while simultaneously offering DC on the PLC channel, since the standard mandates a special dummy value on the control pilot in the DC case. You would have to have a manual AC/DC select switch on the EVSE control panel, which makes this less attractive.

    Personally, I'm not convinced of the practicality of charging in the ~30kW region: from the driver's point of view more power is always better, but the costs of installing the EVSE need to be proportionate and 30kW seems like the opposite of a 'sweet spot'. I think the market for public charging makes sense at the two extremes: low-cost AC charging, installed on a shoe-string and necessarily limited by whatever power is already available in the local electrical supply, and high-power charging that costs a lot to install but is sufficiently attractive that drivers will be prepared to pay for it (and travel from some distance around to use it). 30kW is on the one hand too expensive to install (the EVSE is beginning to get costly, and it almost certainly needs something special by way of an electrical supply), but on the other hand doesn't offer the 'get a full charge while you stop for lunch' benefit that Superchargers do.
     
  12. qwk

    qwk Model S P2681

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    ^^^

    Yes, a 30kw Level 3 charger is pretty stupid. Why install something that costs big bucks, yet charges only 10kw faster than a model S using AC charging? Pretty silly.
     
  13. Banahogg

    Banahogg Member

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    I've found myself wanting a mid-trip boost of 10-20 kWh a couple of times and a 30 kW charger is materially different than a ~6 kW charger - there are a lot more places that I can enjoy spending 30 minutes in the middle of a trip than I can spending 3 hours.

    I think it all comes down to how much a 30 kW DC charger installation would cost. I bet there's a "short stack" supercharger design (3-5 chargers) on an engineer's computer somewhere at Tesla already...
     
  14. stopcrazypp

    stopcrazypp Well-Known Member

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    #14 stopcrazypp, May 7, 2013
    Last edited: May 7, 2013
    I'm well aware of this, but decided to post the 40kW/100kW numbers in order to be consistent with how the slides and my sources specify it. As you point out, that's how CHAdeMO is frequently specified too (the [email protected]=62.5kW)

    The advantage of a Level 1 DC adapter would be that it can be used for both DC AND AC. I bet compatibility with the Tesla connector is one of the main reasons to have Level 1 DC in the first place. It means Tesla only has to include that adapter for both AC and DC charging (it's only slightly different than the J1772 AC one; only some change to the plastic is needed).

    A Level 2 DC adapter would not be usable for AC charging since the AC pins can't be connected/used in parallel, according the the SAE spec which arg has looked at. So it necessarily has to be a different adapter than the one used for AC charging. Tesla can make this adapter optional.

    Disagree on the utility of a 30kW DC charger. Most EVs will not have a 20kW onboard charger (even on the Model S it costs $1.5k extra). Level 1 DC allows even a car with a 3kW or 6kW onboard charger to use 30kW, which is a huge 5-10x boost in speed.

    There are 25kW CHAdeMO chargers (supposedly they cost half as much as 50kW chargers and much less to install) and the places using such chargers would be a prime target for a 30kW SAE DC charger (or connector addition/swap):
    http://www.evdl.org/archive/index.html#nabble-td4659350
     
  15. gregincal

    gregincal Active Member

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    OK, point taken. Assuming there are a few of these chargers and they rev the provided J1772 adaptor to work I suppose I could see it. However, I would assume people would still want the "real" adaptor to do high speed charging. Hard to say at this point which way the winds will blow.
     
  16. arg

    arg Member

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    The Level 1 DC connector shape is exactly the same as the AC one (the DC section of the standard references exactly the same mechanical drawing as the AC section).

    The only differences to the connectors between AC and DC level 1 are that DC requires the facility for the car to lock the connector (the lock is optional for AC), and the EVSE side must have a temperature sensor inside the connector for DC. The lock is presumably required because of the risk of arcing when breaking a DC current. Not clear why the temperature sensor is required for DC only - the risk is just the same for high-current AC as for DC level 1: perhaps they didn't feel able to introduce that requirement retrospectively.

    So, the existing Tesla adapter would work electrically with DC level 1. The only question is whether the locking is sufficient to meet the requirements. The car has the ability to lock the adapter (or Tesla plug on a Supercharger) into the car, but as I understand it the J1772 handle is not locked to the adapter so you can still pull the plug out while charging.

    The way the lock is supposed to work (in the pure J1772 situation) is that the EVSE-side connector latches to the car with the 'hook' on top of the connector (that moves up and down when you squeeze the handle), and then the car locks the latch by pushing out/down a locking pin above the top of the latch so that the latch can't move. I can't see a way for Tesla to make the in-car lock have the effect of locking the J1772 directly, though you could have a sliding piece on the adaptor much like the device described in this thread to ensure that you can't remove the J1772 from the adapter before removing the adapter from the car. Alternatively, I suppose you could do something like having an electrical switch that interrupts the proximity pilot when the latch is raised (and hence responds quicker than the proximity pin itself becoming disconnected).

    But the fact that existing adapters will fit on J1772 DC level 1 (and the car can't tell) seems like a problem.

    Agreed. Regardless of what the spec says, Tesla couldn't provide a passive adapter that connected the pins in parallel since that would leave exposed live pins if you plugged a lev1 or AC plug into this hypothetical adapter. If the spec had allowed commoning, it would have to happen inside the car with a contactor closed only when safe.

    Anyhow, two Telsa adapters, one for "the big plug" and one for "the small plug" is nice and simple.


    BTW, I may have been wrong when I said that you can't automatically select between AC and DC-lev1 on the standard connector: although the DC section of the spec says that "A Control Pilot duty cycle of 5% indicates that digital communication is required and must be established between the EVSE and vehicle before charging. This is required for DC charging.", the AC section says that you are allowed to do digital signalling (the PLC carrier) at the same time as signalling AC availability with the Control Pilot. So possibly the car can talk to the EVSE before starting charging and tell it to change to DC mode. There doesn't appear to be a message defined to do this, but I don't have all the specs to be completely sure.
     
  17. pilotSteve

    pilotSteve Member

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    Because if that what a nearby charger provides, I'd like to able to use it! Hey, its not (yet) a Tesla-centric EV world. So lets all interoperate (and possibly have Tesla leads the 'good EV citizen' charge with an adapter as well as sent the highest bar with SuperChargers).

    If there are good quality electrons available at 20-30 kW I would like to be able to use them!

    Thats why....
     
  18. widodh

    widodh Model S R231 EU

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    Has there been any word about this from Tesla?

    We are starting to see the first Combo Type 2 chargers in the Netherlands and afaik a Combo / CCS adapter would be a lot simpler then the CHAdeMO adapter.

    The EU version of the Model S has a slightly modified version of the Type 2 connector where the car is "coded" for SuperCharging by adding a little pin on top of the Type 2 connector. This way the SuperCharger's connector only fits in a Model S. They could do just the same with a CCS adapter so you can't fry any car with it.
     
  19. Bipo

    Bipo Member

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    The socket has space for that pin, but the actual SC plug is not different from any other Type 2 plug, as yor can see here:

    vrW54LJ.jpg
     
  20. stopcrazypp

    stopcrazypp Well-Known Member

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    I don't expect to hear anything on this front until at least the CHAdeMO adapter is ready (which it still isn't despite the promise of "winter" release) and where there are some more Combo stations installed (which should start happening pretty soon as I've been seeing more and more Combo chargers being UL/CE listed).
     

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