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 or making a Paypal contribution here: paypal.me/SupportTMC

SuperCharger Taper Rates and Quoted mi/hr

Discussion in 'North America' started by Evbwcaer, Jun 2, 2015.

  1. Evbwcaer

    Evbwcaer Member

    Joined:
    Jun 21, 2014
    Messages:
    471
    Location:
    Minnesota
    I have only Supercharged my car one time, but I loaned my car to a friend to make a trip from MN to UT and back. I am glad to see my car getting used and I have been watching his progress on my phone. It seems like the Mitchell, SD SC is slightly faster than the Murdo, SD SC and notably faster than the Worthington, MN SC. For example, the Mitchell SC was "pumping" 233 mi/hr at 233 miles SOC, the others were under 200.

    Are some SC's faster than others, either in KW or in how/when they taper?

    My other observation is that the quoted mi/hr of charge seems to be quite optimistic. Keep in mind I am watching from my phone, so there is probably some lag time, but I would figure the seconds per mile based on miles per hour, then count off for three miles worth and it would almost never be where it should.

    My buddy is totally an EV greenhorn. He rolled into Worthington with 10 miles rated and came into town at 55mph. I was nervous he would not be a fan after that. Now, with some more confidence and shorter SC spacing, he is flying through SD at 80mph with a big smile.

    The consistent rate of the Mitchell SC was remarkable I thought, made we wonder what all of this, "taper" fuss was about.

    Thanks
     
  2. Saghost

    Saghost Active Member

    Joined:
    Oct 9, 2013
    Messages:
    3,038
    Location:
    Delaware
    Miles per hour is averaged over the whole session if I remember right. Since the car charges much faster in the lower part of the battery, you'll see a higher miles per hour at every point in the session if it starts from a lower SoC. You should really be paying attention to kW/kWh rather than mph.
    Walter
     
  3. TexasEV

    TexasEV Active Member

    Joined:
    Jun 5, 2013
    Messages:
    3,796
    Location:
    Austin, TX
    Not to be rude, but you think your buddy driving your car is the "EV greenhorn"? I think there are two EV greenhorns here. First thing you need to do is read the page about supercharging on the Tesla web site:
    Supercharger | Tesla Motors
    if you want to know what all this "taper fuss" is about.
    Then ask your friend who is driving what his state of charge is when he starts supercharging and what kW he is drawing, and if there is another car charging from the paired supercharger. As Saghost said the miles/hr displayed is an average over the session up to that time and is neither the starting rate, the rate at that instant, or the ending rate.
     
  4. Evbwcaer

    Evbwcaer Member

    Joined:
    Jun 21, 2014
    Messages:
    471
    Location:
    Minnesota
    Well Texas EV...you were rude even if you did not try. I am not an EV greenhorn, and I admitted to only using a Supercharger once, so maybe a, "Supercharger greenhorn."

    Here is what the page says:

    "Model S is currently the only EV capable of charging at up to 120 kW, which equates to 170 miles of range in about 30 minutes. There are many factors that affect the actual charge rate, including ambient temperature, utility grid restrictions and charging traffic, amongst others."

    The ambient temps were near the same, (Mitchell had the highest at 92, and was the fastest) the state of charge I looked at was always at 230 rated range, and there were no other cars at any of the SCs, let alone on the same kiosk number. In all cases, except Worthington, the state of charge was about 40 when starting to charge.

    I feel like we can probably rule out utility restrictions because the chargers were all making in excess of 300mi/hr initially, so the power is there. Speak up if you know more.

    At 230 miles of rated range the power going in has been as high as 230mi/hr and as low as about 180mi/hr. Similar temps, no other users, same rated range in the battery, all at Superchargers showing they are capable of well over 300mi/hr.
     
  5. Saghost

    Saghost Active Member

    Joined:
    Oct 9, 2013
    Messages:
    3,038
    Location:
    Delaware
    No no no.

    You're apparently missing what we are trying to tell you about the way the car reports miles per hour of charging. What you actually saw is that "at 230 miles of rated range, the average power going into the car over the entire session to that point was as high as 230 miles per hour and as low as about 180 miles per hour."

    The car reports instantaneous kW, aggregate kWh, and session average mph. The session average miles per hour will vary at any given point in the session based on where you started the charge and how much really fast charging you managed before the taper hit. The average session miles per hour at any given instant is meaningless in assessing your momentary rate of charge.
    Walter
     
  6. cpa

    cpa Member

    Joined:
    May 17, 2014
    Messages:
    941
    Location:
    Central Valley
    Evb,

    Last month I took a road trip from California to Milwaukee, Minneapolis and back, primarily using Superchargers. I believe I Supercharged 37 different times. I changed units from distance to energy so that the display on the touchscreen indicated kWh instead of MPH. At Lovelock I was second fiddle, so received a reduced rate. At Goodland one morning, my initial rate was 53 kWh with a 30% share of charge remaining in the battery. At Glenwood Springs the initial rate was around 70% (at 45% SOC) initially, perhaps due to the fact that it was early in the morning, and the temperature was around 40 degrees.

    All my other charging stops with battery levels varying between 5% and 35% started out anywhere between 113 kWh to 118 kWh, and began to taper around 40-50% (I really did not stay in the car to monitor.)

    I suggest that your friend change the charging units to energy and watch the touchscreen after plugging in. In my cases, the current would ramp up quickly to 114-116 kWh, then fluctuate a little for a few seconds and finally increase to 117 or 118 for some time before starting to taper. A couple of spots never reached that high, but for all intents and purposes a 2-4 kWh reduction is immaterial for adding 40-80% capacity.
     
  7. Evbwcaer

    Evbwcaer Member

    Joined:
    Jun 21, 2014
    Messages:
    471
    Location:
    Minnesota
    Thanks guys, I see what I am missing with the average vs. the instantaneous mi/hr interpretation. I had been figuring the kw by doing the math. Is straight kw the measure to go by, or does it matter regarding charge rate how much comes from amperage vs voltage?
     
  8. Cottonwood

    Cottonwood Roadster#433, Model S#S37

    Joined:
    Feb 27, 2009
    Messages:
    5,062
    Location:
    Colorado
    Use kW, derived from Volts * Amps / 1,000.

    To get instantaneous rate mph charge rate, good round numbers on an 85 are 3.33 (10/3) rated miles per kW for DC charging and 3.0 rated miles per kW for AC charging; the difference is due to AC->DC conversion losses.
     

Share This Page