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How do adapters signal max amperage to UMC?

Discussion in 'Model S: Battery & Charging' started by tls, Feb 1, 2016.

  1. tls

    tls Member

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    I may be in a position to have aftermarket adapters made, at least in small quantity. Not super eager to start cutting apart my spare adapters (and I don't have spares for some) to figure out how they signal max amperage to the UMC. Has anyone done this yet?
     
  2. LuckyLuke

    LuckyLuke Model S P85DL

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  3. Brass Guy

    Brass Guy Member

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    I don't remember where this came from and cannot vouch for accuracy.

    Tesla UMC Plugs Resistance

    40 amps - 9.08k ohms
    24 amps - 33.16k ohms
    16 amps - 75k ohms
    12 amps - 140k ohms

    IIRC, the resistor is between the ground and signal pins.
    In theory, you could turn a 5-15 adapter into a 5-20 by paralleling ~160k ohms on the adapter.
     
  4. RDoc

    RDoc S85D

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    If your numbers are correct, that means that you can increase the current rating but not decrease it. I'd like to be able to decrease it so my home made adapters would signal the correct amperage rather than having to set it on the UI.
     
  5. brkaus

    brkaus Member

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    I would think a 14-50 with dip switches would be the ideal plug. Still have to set it, but could use any adapter in the end of a proper extension and have no risk of the car setting current back to maximum.
     
  6. Brass Guy

    Brass Guy Member

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    I was thinking the exact same thing. So I can't fool the 14-50 adapter to reduce to signal a 30A circuit without wrecking it, you can only increase it with resistors in parallel.
    While I'm sure the 5-15 adapter would have no problem at 16A, I decided it's not worth the risk of melting it with 24A. So I use the 14-50 and dial down in the car. I don't like it, but have no other option for 2 weeks out of the year.
    The best thing to do is to have the correct Tesla adapter (by current rating), then build adapters for whatever outlet you need. All you'd need is the Tesla 5-15, 5-20, (x)-30 and 14-50 adapters; and you could make any adapter you like for it.
    Unfortunately, looking at the web site it doesn't look like Tesla sells any adapters at 30A anymore.

    - - - Updated - - -

    This is an interesting idea. This would be better than my current solution for 30A.
     
  7. RDoc

    RDoc S85D

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    What I'd like is a 14-50 with the resistor for 12A. Then all the other adapters I've made, which plug into the 14-50, could be equipped with parallel resistors to up the allowed amperage to whatever was correct for that adapter.
     
  8. Brass Guy

    Brass Guy Member

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    ... until you plug that 14-50 into a 14-50 and get 12A!

    How would this work? I think you'd have a lead hanging from the signal pin between the 14-50 adapter and the UMC's input, and manually clip whatever resistor you left hanging on your custom adapter.
     
  9. Max*

    Max* Autopilot != Autonomous

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    RDoc actually has a good idea... I like it. You could create a passthrough approach with resistors in parallel, each "box" has a different resistor value.

    Think extension tubes for cameras. You have a small, medium and large tubes for various macro shots, and you can use any of the 3, or stack 2 of them or stack all 3.

    Same would apply with the UMC, the resistor rings, and the modified 14-50 adapter. Without any resistor rings, you'd get 12A (140k ohms), each resistor ring can be color coded to reduce the total resistance when added in parallel to get to the next higher charge rate.

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    Or even simpler, create the modified 14-50, create 1 step-ring and a potentiometer, and have labels to the 3 values you need to achieve the 4 cutoffs
     
  10. RDoc

    RDoc S85D

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    No, you're right, I was thinking the resistor could be in the plug, but obviously that's not true, it has to be from the signalling pin. Wouldn't work.

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    That's a good idea, but unfortunately, I can't claim any credit for it. :crying:
     
  11. DCGOO

    DCGOO Member

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    My objective was to fill in my kit with 120V adapters for cheap (since I hope to never use them). I bought a TT30 (RV 120V connector) to 14-50 adapter. Opened it and rewired the neutral connection. With another 5-15 to TT30 adapter, I can connect to any 120 V outlet and pull up to 40 amps @ 120V. Actually a dangerous level to operate the UMC at continuously. But with the ability on the car console, to explicitly set the current drawn, I can set it to 12, 16, 24, 30 or any other value I want, depending upon what I am plugged in to. Total cost: less than US$30.

    Basically, any time you use the 14-50 UMC adapter, you are limited to 40 amps. But you can turn that down to any level you need. The only problem is you end up with quite long adapter stack. It may have to propped up on something to stay plugged in. But remember this is a last resort hack to get you out of a jam. Not supported at all, but it beats walking!
     

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