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MC240 Current not "sticking" at 24A

Discussion in 'Roadster: Technical' started by Mike Prachar, Mar 14, 2015.

  1. Mike Prachar

    Mike Prachar Member

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    I recently started using the 240V Mobile Charger at home instead of the MC120. The car seems the stay "stuck" at 12A, saying something about remembered for this location, even though I have tried changing the VDS to 24A, resetting to default, etc. I am hitting "OK" and it all looks good until I slide the connector switch at which point it drops to 12A and starts charging. I did run through the test procedure once on the MC240 as well.

    Ideas?
     
  2. Doug_G

    Doug_G Lead Moderator

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    Start it charging FIRST, then dial it up.
     
  3. Mike Prachar

    Mike Prachar Member

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    Once the charging starts, the + / - buttons are greyed out...
     
  4. Doug_G

    Doug_G Lead Moderator

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    Really??? Bizarre. I've never seen that happen.
     
  5. AEdennis

    AEdennis Active Member

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    Weird.

    Mike, do you have OVMS installed? You can change rate there too.
     
  6. supersnoop

    supersnoop Tesla Roadster #334

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    Plug it in it starts charging, then stop the charge and adjust the amps.
     
  7. Lloyd

    Lloyd Active Member

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    Sounds like the pilot signal is broken somewhere. Likely in the MC240, not the car.
     
  8. Mike Prachar

    Mike Prachar Member

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    So, the thing actually tricked me... It's still only going at 12A but I couldn't see that until I left that screen. So weird - the display will say "limited to 24A" just like I want, but as soon as I switch the connector on it goes to 0/12A and then ramps up to 12/12A.
     
  9. gregd

    gregd Member

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    I wonder... The limit is a location-based setting; charge settings are remembered based on where you are. Does your car have a view of the sky, enough for the GPS to know where you are?
     
  10. AEdennis

    AEdennis Active Member

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    My experience with our Roadster is that the GPS settings do provide for a more consistent setting, however, it is easily over-ridden.
     
  11. samcarney

    samcarney Sam C

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    The pilot signal is decided by a diode in the plug end of the MC240. Depending on the orientation (+ / -) of the diode, charging will be limited to 24 or 40 amps. if the diode is missing or defective charging will be limited to 12 amps.

    This is how it is with the Roadster Foundry Mobile Connector. The diode is located in the plug itself. I don't know if the MC 240 has the capabilty to use different plugs NEMA 10-30, 5 -20, etc. as the RFMC. But as Lloyd has stated the problem is more than likely with the MC240.
     
  12. gregd

    gregd Member

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    Right. But what if it acquires a fix right after you set the higher charge rate, then it acquires a lock and figures out where it actually is, re-setting the charge rate based on position. That would be a bug, yes, but not impossible. The test would be to turn on the car outside somewhere, and let it hum quietly to itself for a few minutes (to acquire a lock), then set the charge rate, then slide the charge switch on the connector. If I'm right, that should work. Slim chance, but easy to try.
     
  13. samcarney

    samcarney Sam C

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    If you have access to an MC120 it should charge at 15 amps 120 volts.

    Also have you tried taking the Roadster to a different location to charge? This would determine if it is GPS related.
     
  14. Mike Prachar

    Mike Prachar Member

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    The screen does mention that it is the current is set by the location. I can get that same message to say "User Limit 24A" but it reverts as soon as I throw the switch. I did, initially use the MC120 to charge at this same location (my house) so at some point 12A was appropriate.

    The car is in the driveway and should have no problem getting a GPS lock.

    In order to try the MC240 elsewhere I will need to dig up some adapters....

    Does anybody know if it needs all four conductors for the sensing to work properly? My 240V outlet only has 3 (which has not been a problem for other EVSEs.)
     
  15. supersnoop

    supersnoop Tesla Roadster #334

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    It only needs two hits and a ground; it doesn't require the neutral wire. It really does sound like the pilot signal isn't working.
     
  16. samcarney

    samcarney Sam C

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    **The Neutral is not used all you need are 2 hots and a ground.

    Also; try opening and closing the chargeport door several times to reset everything. Like 8 or more times
     

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