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J1772 Hydra - charge two vehicles with one charger

Discussion in 'Charging Standards and Infrastructure' started by nsayer, Mar 2, 2014.

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  1. nsayer

    nsayer Member

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    Last year as a sort of adjunct to the OpenEVSE project, I created a device called the J1772 Hydra. It's designed to allow two plug-in vehicles to share a charging station, but to do so safely and in full compliance with the J1772 specification.

    I haven't posted about it here before because it's less of a perfect fit for Tesla owners, but it's conceivable that there are Tesla owners with more than one EV at home and a J1772 EVSE that they use for both.

    The Hydra is tailor made for households that have a time-of-use electricity tariff, such as PG&E's E-9, which encourages them to charge overnight. With the Hydra, you don't need to switch the plug from one car to the other at 2 AM.

    It's an open hardware project, like OpenEVSE. Plans and firmware source code are freely available. Also, I have a square market store where I sell the boards as both "quick kits" (which is the board with all the surface mount components preassembled and preprogrammed, and with all through-hole parts for you to install yourself) and assembled and tested.

    For more information, check out the Hydra wiki page at https://code.google.com/p/open-evse/wiki/Hydra
     
  2. Kipernicus

    Kipernicus Model S Res#P1440

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    Sounds like it is still one car at a time though right? Or could you have two 3kW cars charging simultaneously off one 6kW source?
     
  3. drees

    drees Active Member

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    That's exactly what it allows. Assuming this is plugged into a 30A EVSE, If two cars are plugged in and charging, each is given a 15A pilot signal. If one car is plugged in, it gets a 30A pilot signal. And if there is only one car charging, it will get the entire 30A.

    This works like the dual-head ChargePoint CT4000 which gives you two J1772 plugs hooked up to a 40A outlet.
     
  4. DEinspanjer

    DEinspanjer Member

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    Wow.. I hope one day to have the fortune to wish for a Tesla HPWC version of this so I could plug my S and my X in and let them both charge at 40A over night. :)
     
  5. mitch672

    mitch672 Active Member

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    No reason you can't, it's just the Tesla connectors are not available currently. You could build a 75A J-1772 OpenEVSE, then on the (2) J-1772 cables that come from the hydra, just use the Tesla J-1772 to Tesla adapter. The protocols are the same... If Tesla where to offer the female inlets, and male connectors, you could build it Tesla specific.
     
  6. drees

    drees Active Member

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    Yep, what Mitch said.

    There is a way to do it with the HPWC, but you'd have to buy two of them and hack them up for parts.

    Cut off the plugs on each HPWC, hard wire one HPWC to the Hydra (source an appropriate length of 80A EVSE type cable or hard-mount the Hydra and run individual strands in conduit) and attach both HPWC plugs to the Hydra. Depending on how much cable length you need, you could just have unequal lengths plug cables coming out of the Hydra as well if that works.

    Power handling components in the Hydra would have to be sized appropriately for 80A continuous instead of the typical 30A continuous.
     
  7. andrewket

    andrewket 2014 S P85DL, 2016 X P90DL (soon 100)

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    Will the device change the pilot signal while a vehicle is charging? For example, what if two cars are plugged in and both are charging at 20A on a shared 40A circuit. When car one finishes, will the pilot signal change to 40A on car two? And if it does, will EVs today accept that change mid charge? Or would the charging session on car two have to be restarted for the change to take affect?
     
  8. drees

    drees Active Member

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    The pilot will increase when the 2nd car stops charging. Some cars may not automatically increase the charging rate. I believe someone reported that the Model S was affected here?
     
  9. Cottonwood

    Cottonwood Roadster#433, Model S#S37

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    You could actually do it with one HPWC, with the resulting Hydra having one Tesla connector and one J1772:

    1. Remove cable with Tesla charge connector from the HPWC.
    2. Connect HPWC output to Hydra input with cable that will carry 80A for charging plus appropriate size ground and pilot.
    3. Use the HPWC cable from #1 for one Hydra output.
    4. Buy a 75A J1772 cable for the other Hydra output. Have Hydra controller limit this connection to 75A.
     
  10. mitch672

    mitch672 Active Member

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    Sure, all doable. The 80A J-1772 cable needed to go from the HPWC to the Hydra used to be listed on eBay for $8.99 per foot, I believe hcsharp sells it. The ITT 75A J-1772 cables seem to have disappeared from earth, but they where in the $250 range when last availble. You would also need 2 heavy duty 80A contactors, those run about $120 each. Hardwiring the HPWC to the Hydra is about the only way you can really do it, since Model S inlets are not readily availble (and who knows how much it would cost as a spare part from Tesla, plus you would need another cable assembly as well, or a 2nd ITT 75A J-1772 cable and use the Tesla adapter with it)
     
  11. hcsharp

    hcsharp Active Member

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    No longer on ebay but I still have a little of this. If you want some send me a PM. It's UL EVE, 80A, 105C cable with 2 signal wires, 2 power wires, and ground.

    I believe it's still possible to get the ITT 75A cables, but they are closer to $400 with connector and 25' cable. Does anybody know who's making the 80A J1772 connectors that ClipperCreek is using? Are they making those themselves?
     
  12. drees

    drees Active Member

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    Nice, I love continuous iteration and group collaboration. :)
     
  13. miimura

    miimura Active Member

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    If you're doing this for your own garage, why not cut the HPWC cord 12" from the case exit and wall-mount the Hydra box just below the HPWC, hard wiring it in. Then use the rest of the HPWC cord and attached handle for a Tesla vehicle and buy a new J1772 cord for the other car. Since you can modify the Hyrda firmware, you could use a 30A J1772 and set the current limit for that output accordingly.
     
  14. Cottonwood

    Cottonwood Roadster#433, Model S#S37

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    No need, just need a couple of #3 or #2 cables for power, some #6 ground, and a pilot wire in a conduit.

    If you look closely, the ClipperCreek CS-100 is limited to 75A max current; interesting...

    Because if you don't cut the cord, you can put the HPWC back together again like it came from Tesla.
     
  15. hcsharp

    hcsharp Active Member

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    They are manufacturing newer units that are rated for 80A. The older CS-100 used the ITT cable and connector which is rated for 75A. I haven't seen an 80A unit in person (only pictures) and I'm curious who is making the 80A connector. Schneider is also advertising a version of their EVLINK series rated for 80A. I suspect both of these companies are having the connectors custom made for them.
     
  16. cwerdna

    cwerdna Active Member

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    Hope the OP doesn't mind, but I'd imagine that he was the speaker re: the Hydra at SF BayLEAFs meeting: February 2014 - YouTube. At ~0:10 mark, some links will pop up that will let you skip to the J1772 Hydra portion.
     
  17. nsayer

    nsayer Member

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    Oh wow! Yes, that's me, and I had not seen that video! Thanks for the link!

    Also, if anyone is on the fence, I'd like to also say that if you're in the SF Bay Area on April 12, there will be an OpenEVSE / Hydra build workshop at the Hacker Dojo in Mountain View. I'll be there to help anyone build themselves whatever they need.

    Interestingly, between the last time I had checked back in on this thread and now, it went from no replies to 2 pages!

    Most of what people said is correct:

    1. The Hydra can be built with any inlet and outlet current capacity desired within the range allowed by the spec (up to 80A). The firmware can separately limit both the inlet and outlet current capacity so that, for example, you can have two 30A outlets and a 50A inlet. When both cars are charging, the pilot would be 25A, but when one car stops, the other would pop up to 30A.

    2. There are two modes the Hydra can use - sequential or shared. In shared mode, both cars share the host EVSE. In sequential mode, one car gets a full power pilot, and the other gets nothing. When one car finishes, the pilot is moved over to the other car and they "pass the baton."
     
  18. nsayer

    nsayer Member

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    ... assuming that you've got a host EVSE that's >=50A.

    If it's less than 50A, then its ampacity would be the limiting factor, of course.
     
  19. davewill

    davewill Member

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    The LEAF and I think the Roadster (may have been finally fixed) fail to charge with an 80a pilot, so a lot of CS-100s, when installed as public chargers, end up @ 70a.
     
  20. TEG

    TEG TMC Moderator

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    I was at the LEAF meeting where the Hydra was presented. I was impressed with the level of careful consideration the designer gave to all of the possible usage scenarios. Not sure how many people actually need something like this, but if you do, it seems like he is trying to do it right.
     

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