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Change charging settings (amps) when plugging into wall

Discussion in 'Model S: Battery & Charging' started by tmc2015, Jun 5, 2015.

  1. tmc2015

    tmc2015 Member

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    When I plug my car into a wall outlet, do I need to change my settings to the appropriate amperage for that circuit? If my setting is at 40amps but I'm plugged in to a 20amp circuit, will my car try to take more juice and trip the circuit?

    Tried to find an answer on then forum first.
     
  2. arg

    arg Member

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    _IF_ you use the Tesla UMC with the correct adapter for the type of outlet, or a similar EVSE (=charging cable) that's made specifically for the type of outlet, then no - it's automatic. The EVSE tells the car the maximum amps it is allowed to draw.

    If you make up your own cable adapters - say you keep the 14-50 adapter on the end of the Tesla UMC but then make up a little extension cable with another type of plug on it - then the car will think it's connected to a 14-50 and so try to draw up to 40amp. This is one of the reasons Tesla say "no extension cables" in their documentation.
     
  3. gnxs

    gnxs Member

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    I have a Clipper Creek HCS-60 that is supposed to provide 48A. Before I picked up my MS, we were only using it to charge my wife's Ford Focus EV. The first time I plugged it into my Dual Charger P85, it soon tripped the breaker. I then manually set the Amperage in the car to 48A and it tripped it again. Then down to 40A, same thing. I eventually had to go down to 32A so the breaker wouldn't trip.

    I'm not sure if this might be related to the amount of power going to the wall charger (I believe there is 60A dedicated to the Clipper Creek, but I need to verify the wiring is all correct since I haven't had an electrician out to look at it. Either way though I figured the car would adjust the amperage draw down to what the charger was able to provide w/o tripping the breakers. I am using the Tesla J1772 adapter on the end of the Clipper Creek J1772 cable.
     
  4. tga

    tga Active Member

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    That's not really correct. The car will dial back the charge rate if it sees a "significant" voltage drop as the current ramps up, or for other unspecified reasons that resemble an arc fault (the whole algorithm is proprietary and undisclosed). But it can't detect all issues, such as the EVSE being installed on too small a breaker.

    Any J1772 EVSE (including the HPWC or a Clipper Creek unit) is configured with a max advertised current. Any car will try to pull the minimum of the EVSE's advertised max and the car's charger(s)'s max (in your case, ~30A on the FFE or 48A on the MS). But the car "trusts" that the EVSE can deliver the advertised current, which assumes that the installer used wire and a circuit breaker with sufficient capacity to handle the load.

    Depending on the type of wire used, your HCS-60 needs 4 or 6 gauge copper and a 60A breaker. You may also have loose connections at the breaker terminals, causing the breaker to overheat and trip.
     
  5. arg

    arg Member

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    In which case, there's something very wrong with your installation and you should really get it checked out rather than relying on dialing it down in the car - although the car is supposed to remember the setting, it can't be relied upon to do so.
     
  6. gnxs

    gnxs Member

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    Thanks for the info. I'm scheduling an electrician to come look at it.

    The 240V 60A wiring was run to the garage years ago in case I needed the power for something (e.g. a large compressor) and was left capped in a junction box. I utilized that wiring (which runs directly from a connected pair of 30A breakers in the box). I'm not an electrician so I don't know:

    1) Exactly what power I'm really getting
    2) What the wiring will support

    - - - Updated - - -

    I am scheduling a pro to come out ASAP. Thanks.
     
  7. arg

    arg Member

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    I think that's your problem. A 30A paired breaker is a 30A 240V circuit, not a 60A circuit (single breakers are 120V circuits). So even at 32A you are overloading it.

    Of course it's possible that the wire was installed to support 60A and it's just the breaker undersized, but more likely you need new wiring to use the EVSE at full power.
     
  8. mknox

    mknox Well-Known Member

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    Nope. Unless you specifically dial it down, the car will attempt to draw the maximum that the particular adapter you are using will allow, and will pop the breaker if it is over the capacity of the circuit. Having said that, the adapter, receptacle, wiring and breaker should all be matched for capacity if installed correctly and to code.

    This comes in to play with home-made adapters. For instance, you may have a 20 amp, 240 volt outlet, but there is no corresponding Tesla adapter for the UMC. What do you do? Some would make up a cheater cord with a 20 amp plug on one end and a 14-50 outlet on the other. Plug the Tesla 14-50 adapter into one end of the cord, and plug the other end into the wall. Tesla will think it can safely draw 40 amps, but when the 20 amp breaker sees that, it will trip. What you need to do in this case is dial the car down to 16 amps (80% of the 20 amp circuit) and it will work. The car will also store these charge settings based on GPS coordinates, so if you are doing this regularly at the same location, you don't have to dial it down each time.
     
  9. TexasEV

    TexasEV Active Member

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    A better idea-- use the Tesla UMC 5-20 adapter and plug that into a 5-20R to 6-20P adapter. That way the car knows its a 20A circuit and sets the draw at 16A automatically, but you get 16A at 240V. EVSEadapters.com now makes a 5-20R to 6-20P adapter for that purpose (at my suggestion). Just make sure you label the adapter "for Tesla only" so no one tries to plug anything else into it!
     
  10. MorrisonHiker

    MorrisonHiker Beta Tester

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    This is the route that I plan on taking with my 3rd garage bay where there is a 6-20 outlet installed. The other two bays will get 14-50 outlets if the "Tesla Recommended electrician" ever gets back to me with an estimate.
     
  11. gnxs

    gnxs Member

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    Sounds like you're likely correct. I'll dial it down in the car to 29A until the electrician gets out to verify what I've got. Looks like I'll need him to run a dedicated 60A circuit to the Clipper Creek.
     
  12. MorrisonHiker

    MorrisonHiker Beta Tester

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    Wouldn't it need to be set to 24 amps (continuous load) or does Telsa already take that into account?
     
  13. No2DinosaurFuel

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    IF I have existing wires for a 40A at 240, I am guessing I need get the NEMA 14-30 and use the UMC? But that would mean I will be limited to 20A charging from my UMC? Is there a way I can get 30A current draw from the tesla without buying EV J1772 charger?
     
  14. Cottonwood

    Cottonwood Roadster#433, Model S#S37

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    You will need to dial the car back to 24 Amps. The most that the NEC allows for a continuous load is 80% or the breaker rating for conventional breakers. You may be able to squeeze a little more than 24 Amps before the breaker pops, but why risk it. Dial back to 24 Amps until you get a correct 60 Amp circuit to the J1772; that will then correctly offer 80% of 60 Amps or 48 Amps on the J1772 pilot signal to the car.

    Good Luck!
     
  15. thimel

    thimel Member

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    For your 30 amp breaker you should dial it down to 24 amps, not 29. For a continuous load, circuits should only be run at 80% of their capacity.
     
  16. tmc2015

    tmc2015 Member

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    So the answer is yes and no. I am going to stay at a hotel that has a plug, but I don't know what the amps will be. I'd rather not inconvenience them by tripping it. They could have a 14-50 but only be using a 30 or 40 amp circuit, for example. I will examine the plug and area and will ask of course. If inconclusive, I will dial it back to 24 in my car to be safe. Thanks everyone for the additional info.
     
  17. MorrisonHiker

    MorrisonHiker Beta Tester

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    #17 MorrisonHiker, Jun 5, 2015
    Last edited: Jun 5, 2015
    If they have a 14-50 outlet installed, I would think it should have a 50 amp breaker and allow you to charge at 40 amps continuous load. Then again, I'm no expert. I'm sure more knowledgeable members will provide the answer below.
     
  18. davewill

    davewill Member

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    #18 davewill, Jun 5, 2015
    Last edited: Jun 5, 2015
    It would be 24a...but you can't put a 14-30 on your 40a circuit (unless you switch to a 30a breaker), you'd have to use a 14-50. Unfortunately one of the limitations of the UMC is that you can't tell it that you have only a 40a breaker on your 14-50. Your only option in that circumstance is to dial the car down to 32a. That's one of the reasons I didn't get one of the J1772 converted UMCs for my RAV. I have the same setup (40a circuit on a 50a outlet) at home and the RAV doesn't even have a way to dial down the current.
     
  19. mknox

    mknox Well-Known Member

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    Depends. In Canada, 14-50 outlets are allowed to be wired for 40 amps (40 amp breaker and appropriate sized wiring) for stove outlets. Not sure if the US NEC allows for this, but generally US and Canadian regulations are very similar. If it's wired this way, you can only charge at 32 amps.
     
  20. TexasEV

    TexasEV Active Member

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    If you have a 40A circuit you could hard wire a HPWC and set the DIP switches appropriately for that circuit to draw 32A.
     

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