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HPWC charge indicator?

Discussion in 'Model S: Battery & Charging' started by ai4px, May 30, 2018.

  1. ai4px

    ai4px Member

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    Techhie people.... is there any dry contact inside the HPWC gen2 that indicates it is actively charging? My goal is to hook another non-tesla EVSE for my other car to the same 50amp circuit and have the HPWC inhibit the other EVSE from allowing the other car to charge. The other EVSE is a siemens versicharge and it has a dry contact input to inhibit charging.

    I get home hours before the wife and drive a shorter distance so it's ok if my car isn't fully charged. Her MS must take precedence once she gets home. My original plan was to get two HPWC, but I'm about to get a price I can't refuse on the siemens unit.

    I suppose my other option is to hook up a small 220v relay inside so that when power is applied to the cordset, it gives me that dry contact I'm looking for.
     
  2. Ande

    Ande Member

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    No, there is not.
    The wall connector does have a more sophisticated power sharing protocol.
    It's trivial to have a microcontroller programmed in a way to emulate such a digital output based on that data.
     
  3. Rocky_H

    Rocky_H Active Member

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    The really sweet setup would be two Tesla wall connectors with their power sharing, but get one of them from Quick Charge Power that has its cord switched out for a J1772. Or, you could get a set of the Share2 units from Clipper Creek, but they're kind of expensive at $1,500.
    32A Level 2 EVSE Share2® HCS-40 Bundle| ClipperCreek

    But since you said you're getting a great deal on that Siemens unit, I think the only really code compliant way to install those would be to get an A/B transfer switch installed on the line, so they can't try to run on the circuit at the same time.
     
  4. davewill

    davewill Member

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    Well I like the idea. The 240v relay should work great. That would be the surest and cheapest way of doing this. I wouldn't fool around with trying anything more complex, and see no reason for a transfer switch.
     
  5. gregd

    gregd Active Member

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    Um, so your thought is to have the relay cut off power to the first car when the second one (the Tesla) plugs in? I think that's kind of abrupt. The car's not going to like it, and it will be hard on the relay because you're doing it under load.

    It might be more effective to wire the relay into the "Pilot" line, manipulating it to command the first car to reduce or stop its charging. Disconnecting the pilot line should stop it from charging, without unceremoniously yanking the plug. For extra credit, you could manipulate it (I forget exactly now) to command the car to drop to, say, 6 amps, allowing it to trickle charge a bit, while the Tesla charges at full speed.
     
  6. davewill

    davewill Member

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    The Siemens has an input that is meant for an external timer. That's what the relay would be triggering. No sudden cutoffs.
     
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  7. ai4px

    ai4px Member

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    Yep.... that's what I'm talking about.... Siemens versicharge has a dry contact input to stop charging in an orderly manner. It also has an output to indicate charging. I think if you cross connected two of them, the one that started charging first would continue charging until done at which time the other unit would begin.

    I installed my HPWC today and had a look around inside. Looks like I might be hooking a 220v relay up across the contactors inside that go to the charge cord and using that relay as the needed dry contact. I'll check when the wife gets home with the MS.
     
  8. ai4px

    ai4px Member

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    Oh and speaking of abrupt cessation of charging.... what about dryer buddy? As soon as you start your clothes dryer, dryer buddy kills 220v to the EVSE.
     
  9. gregd

    gregd Active Member

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    Ah, missed that. Yes, that's perfect.
    On the other hand, this isn't good. Probably meant to be a fail-safe in case you're still charging the car, vs the normal operating mode. But good to know!
     

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