TMC is an independent, primarily volunteer organization that relies on ad revenue to cover its operating costs. Please consider whitelisting TMC on your ad blocker and becoming a Supporting Member. For more info: Support TMC

Average MPH on 13amp UK plug

Discussion in 'Charging Standards and Infrastructure' started by Fellsteruk, Mar 13, 2018.

  1. Fellsteruk

    Fellsteruk Member

    Joined:
    Feb 24, 2018
    Messages:
    223
    Location:
    North West, UK
    Hi,

    What’s an average MPH I’d get with a MX75D plugged into a normal 13amp uk plug? I read 2miles per hour of charge is it really that low?

    Thanks
     
  2. mblakele

    mblakele (つ ͡° ͜ʖ ͡°)つ

    Joined:
    Mar 7, 2016
    Messages:
    701
    Location:
    SF Bay Area
    According to tesla.com the "domestic adapter" charges at 2.3-kW. They say that's 6-mph, but they don't say for which vehicle. The math looks about right if it's for the Model S. The Model X would be a bit less, maybe 4-5 mph. Of course those are rated miles and YMMV.

    https://www.tesla.com/en_GB/support/home-charging-installation
     
    • Like x 1
  3. arg

    arg Supporting Member

    Joined:
    Aug 22, 2012
    Messages:
    1,025
    Location:
    Cambridge, UK
    6-7mph is about right for Model S in the UK. Model X should be at least 5. If you were hearing 2mph, that may have been from the USA with 120V power (and even then would need other unfavourable conditions to get it that slow). Alternatively, it could have been someone who plugged in to a 13A socket and looked at the MPH on the display straight away, without leaving enough time for it to settle on the final figure. In general, the charging mph on the display is highly misleading and you are better to look at the power figure and make your own estimate of how that turns into miles.
     
    • Like x 1
  4. Fellsteruk

    Fellsteruk Member

    Joined:
    Feb 24, 2018
    Messages:
    223
    Location:
    North West, UK
  5. Ames

    Ames Member

    Joined:
    May 27, 2013
    Messages:
    549
    Location:
    Abu Dhabi, UAE
    I can confirm 6-7 mph on a UK domestic plug.
     
  6. cizUK

    cizUK Member

    Joined:
    Mar 13, 2017
    Messages:
    186
    Location:
    UK
    #6 cizUK, Mar 15, 2018
    Last edited: Mar 15, 2018
    13A * 230V = 2990W = 3kW
    259 (NEDC) miles / 75kWh = 3.5 miles / kW
    3kW * 3.5 miles/kW = 10.5 mph

    237 (EPA) miles / 75kWh = 3.2 miles / kW
    3*3.2=9.5 mph

    213 (realistic) miles / 75kWh = 2.8 miles / kW
    3*2.8=8.5 mph

    Of course, you may have to account for losses, I don't know how significant it is.
    Have I got the calculations right?

    But Tesla's plug must only have a 10A fuse to get 2.3 kW
     
  7. arg

    arg Supporting Member

    Joined:
    Aug 22, 2012
    Messages:
    1,025
    Location:
    Cambridge, UK
    The calculations are correct, but some of your assumptions are optimistic.

    Although a "13A" plug, experience dictates that they aren't suited to continuous operation at that current, and manufacturers of EVSE (including Tesla with the UMC) have adopted 10A as the safe limit.

    The NEDC range is hopelessly optimistic and no use for practical purposes. On the other hand, you are assuming that a "75" has 75kWh of usable battery, when in fact a portion of that capacity isn't available for use, so your "realistic" calculation is actually pessimistic. I use 333Wh/mile (or 3 miles per kWh) as a rule of thumb - it's an easy figure to work with, and actually matches very closely to my lifetime average shown in the car. I have the displays in the car set to "typical" rather than "Rated"(=NEDC), and I believe the "typical" calculation uses a slightly lower figure, about 300.

    There is an overhead on charging - a (quite small) percentage overhead on the power conversion, but also a fixed overhead for running all the computers/cooling systems/etc that have to be powered up to enable any kind of charging. As a round number, deducting 1A for this (230W) is about right.

    So:

    Actual current drawn from 13A socket: 10A
    Deduct 1A for fixed overhead: 9A
    Convert to watts at 230V: 9 * 230 = 2070W
    Convert to MPH at 333Wh/mile = 2070/333 = 6.2MPH
    Convert to MPH at 300Wh/mile = 6.9MPH
     
    • Informative x 1
  8. cizUK

    cizUK Member

    Joined:
    Mar 13, 2017
    Messages:
    186
    Location:
    UK
    Yes, that makes sense, although Tesla still says 2.3kW when you are saying 2.07kW
    Anyway, it all gives very similar figures
     
  9. arg

    arg Supporting Member

    Joined:
    Aug 22, 2012
    Messages:
    1,025
    Location:
    Cambridge, UK
    They are quoting the input power (as will be displayed in the car) without deducting for overheads - so 2.3kW will be drawn from the mains, but only about 2.07kW of it ends up in the battery (and those figures have too many digits of precision!).
     
    • Helpful x 1

Share This Page

  • About Us

    Formed in 2006, Tesla Motors Club (TMC) was the first independent online Tesla community. Today it remains the largest and most dynamic community of Tesla enthusiasts. Learn more.
  • Do you value your experience at TMC? Consider becoming a Supporting Member of Tesla Motors Club. As a thank you for your contribution, you'll get nearly no ads in the Community and Groups sections. Additional perks are available depending on the level of contribution. Please visit the Account Upgrades page for more details.


    SUPPORT TMC