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Setting charge current

Discussion in 'Model S: Battery & Charging' started by ev-soon, Aug 14, 2015.

  1. ev-soon

    ev-soon Member

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    I've read many threads, but as a not-yet-owner, I just want to be sure.
    When scheduling a charge window (for TOU or to avoid demand peaks) it is possible to set the time, and the maximum current drawn - correct?
    Given yes, are there any limitations on how low the current can be set, and any restrictions placed on a single charger configuration (other than the obvious 40Amp max)?

    Thanks for your help guys (questions will spike in a few weeks or so once I actually have it I am sure - but after that hopefully not too many more)!
     
  2. Razlak

    Razlak Member

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    Yes, you set both the charge time and max current to use, and the car remembers those settings at that GPS location.
     
  3. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

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    Setting below 30 is inefficient, so it's best to charge somewhere between 30 and 40.
    You can set the start time. No TOU where I live, but setting the start time so that charging ends shortly before driving keeps the battery SOC as low as possible for a longer period of time (hot weather), and keeps the battery warmer (cold weather).
     
  4. One Gear

    One Gear Member

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    #4 One Gear, Aug 15, 2015
    Last edited: Aug 15, 2015
    I often charge at 10 to 12 amps at 240 volts during the day so I can take full advantage of our solar power, which usually produces between 2 and 4 kWh depending on time of year and weather. Is that not good? Why is setting below 30 amps inefficient?
     
  5. paulkva

    paulkva Member

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    Maximum varies based on what you're plugged into, of course. A "standard" 240V NEMA 14-50 outlet on a 50A breaker maxes out at 40 amps. HPWC with dual chargers on a 100A breaker will go up to 80 amps.

    I can set my car as low as 5 amps when it's plugged into a 120V outlet. Not generally recommended, of course; at that point you're probably barely maintaining charge and not likely to be adding anything significant.
     
  6. scottm

    scottm Active Member

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    You're fine with that strategy. If you are backfeeding the grid so there is headroom from grid if sol drops below 10A then the car will maintain pulling your setting. If it sees a voltage drop from your source it will start kicking down Amps automatically, going lower than your setting. If a kickdown doesn't bring voltage back up, the car will shutdown charging altogether and warn you have a bad source and check your extension cord or whatever..
    The efficiency comment is just that.... it's a truth that higher charging powers result in better conversion rate of sourced power to stored power, as measured from the source.

    - - - Updated - - -

    5A 120 is enough to keep the electronics warm on a cold day by running some current through but I'm not sure of the charging value of such low input... I think you do better than break even but looking at a full charge taking maybe 2 weeks for an 85 pack.
     
  7. ev-soon

    ev-soon Member

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    Thanks for the responses.
     
  8. mknox

    mknox Well-Known Member

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    Unless you only have a 20 amp circuit (16 amps delivered). :wink:
     
  9. Brass Guy

    Brass Guy Member

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    As far as I know, when the car detects a voltage drop it sets the current to 75% of the maximum allowed for the adapter being used. So if you've set it to 24 amps (but using a NEMA 10-50), when it detects a voltage drop it will set it to 30A. This happened to me over the summer. There has been at least one software update since, so maybe this is changed.

    To answer the OP, the charge current can be adjusted by increments of 1A. It is geo-aware and will automatically charge at the current you set at a given location.
     

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