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Automatically sense outlet capacity?

Discussion in 'Model S: Battery & Charging' started by johnr, Feb 19, 2013.

  1. johnr

    johnr Member

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    Is it true that the Model S can somehow sense the current carrying capacity of any outlet it's plugged in to, and adjust the charging rate correspondingly? I know the Roadster came with pigtails that would send a pilot signal to the car's charger so it will draw the right amount of current, or it could manually be set if needed. But I've read that the Model S can somehow "sense" the breaker rating on its own. Anyone have any information on this?
     
  2. DCWitt

    DCWitt Member

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    This is just what I have read somewhere, so do not take for fact.... But I think it starts the charge process, monitors voltage and drops charge amperage if it see >x voltage drop.
     
  3. ElSupreme

    ElSupreme Model S 03182

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    The adapter you put on the UMC sends the information to the car. The car only knows what adapter is being used.

    For J1772 there is a protocol where both the car and the EVSE tell each other what they want power wise.
     
  4. Doug_G

    Doug_G Lead Moderator

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    There are different plug styles for different power levels. This is something required by the electrical code.

    All Tesla did is provide different adapters for the UMC. The adapter tells the UMC how much power is available from that type of socket.

    So, in a way, yes... but it's based on the type of plug.
     
  5. TEG

    TEG TMC Moderator

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    Besides, I think a breaker is supposed to let full current through (keeping voltage nearly constant) until the point that it trips.
    I would think the breaker would pop before some "auto current device" could make adjustments to the charge rate.
    (But I could be wrong about this.)

    Really, with all the advanced technology in the world, I am surprised that we don't have outlets that advertise their current capability to devices plugged into them. That technology is long overdue. Also, each device added to the circuit should tell the other devices what it is using so in sum they don't overload the breaker or wiring. (For instance the car charger could reduce load while the garage door is operating...)
     
  6. Babylonfive

    Babylonfive Power12

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    Wife: "Why are clothes in the dryer still wet?"

    Husband: "I ran some extra errands today..."

    Wife: "Oh, OK. That makes sense"
     
  7. FlasherZ

    FlasherZ Sig Model S + Sig Model X + Model 3 Resv

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    No, it does not and cannot. Voltage drop is not an accurate method, because in long circuits (think end of parking lot), you'd end up not reaching full current, and for some short circuits you'd be smoking the wires before it properly fell off.

    - - - Updated - - -

    Basic breakers have no idea of voltage. They use two different types of protection: thermal and electromagnetic. Thermal breakers use a bimetallic strip that, given enough current through it for a length of time will cause it to heat up and eventually break the circuit. Electromagnetic protection pulls the breaker to the tripped position when the current through it draws the breaker open.

    There are very few truly "variable" loads like we see with model S that could take advantage of that, so it becomes a cost question at that point. In terms of devices communicating with each other to draw loads, this is probably one of the best use cases, but it's still rare that we trip circuit breakers nowadays, and the cost likely wouldn't be justified.

    - - - Updated - - -

    Something appropriate for this conversation, I think:
    You can't plug in a 2 with a 6!
     
  8. tezco

    tezco Sig P85

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    As previously mentioned, the adapter at the end of the UMC cable "communicates" with the UMC to set the maximum allowable current draw. Sometimes out of code installations may have undersized wiring running to the receptacle, which could "mislead" the UMC and result in the car attempting to draw an unsafe level of current. Should your find that be the case, you can adjust the current draw downward with the controls on the touchscreen. Homebrew plug-style adapter/converters can also "mislead" the UMC, so remember to be cognizant these potential pitfalls at unfamiliar charging stops.
     
  9. johnr

    johnr Member

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    Well I guess that answers my question. So I guess that means the model S determines optimal charging rate based on which adapter is used, just like the Roadster. Then it may be necessary to manually adjust the current draw when using homebrew adapters to charge at those more obscure outlets. Thanks everyone.
     
  10. FlasherZ

    FlasherZ Sig Model S + Sig Model X + Model 3 Resv

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    Be sure to read the FAQ thread:
    FAQ: Home Tesla charging infrastructure QA
    ...for reasons you want to avoid home brew adapters.
     

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