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Supercharger charge rate drops over time

Discussion in 'Model S: Battery & Charging' started by Treading water, Dec 2, 2013.

  1. Treading water

    Dec 2, 2013
    Santa Barbara ca
    Every time I use a supercharger it starts out at an awesome 80+kW charge rate! then slowly decreases. I'm now charging in Barstow. It started out at 90kw but it's down to 24kw at 246 miles of range. Can this be avoided if I hop chargers, and if I do that will it damage the battery? Anybody know why this happens?
  2. stevezzzz

    stevezzzz R;SigS;P85D;SigX;S90D;XP100D;3LR

    Nov 13, 2009
    That's completely normal, a result of the Supercharger ramping down the charge rate, on purpose, to take care of your battery pack. The closer you are to a full charge, the slower the charge rate. The tapering really becomes noticeable around 80% SOC, if I recall. Ideally, with Superchargers every 150 miles or so, you'd be heading off to the next one before the taper really kicks in.
  3. pgiralt

    pgiralt Supporting Member

    Jun 16, 2013
    Cary, NC
    Take a look at the Supercharger page on It describes what you are seeing. Attaching a snapshot below. Basically, the last 20% takes about the same amount of time as the first 80%.

    Screen Shot 2013-12-02 at 7.31.03 PM.png
  4. Cottonwood

    Cottonwood Roadster#433, Model S#S37

    Feb 27, 2009
    Also, see my measured data at Finally 120KW Supercharging! - Page 8

    An incredibly important point to remember is that the mph displayed is the average of your session. As the charge rate tapers, this will always give you a higher number than the actual, most-recent charge rate. To get your actual, most-recent mph, you need to multiple Volts times Amps and divide by 300 W-hr/mi, V*A/300.
  5. bob_p

    bob_p Active Member

    Apr 5, 2012
    Based on my experience with recent trips using the Texas superchargers, ideally, I will leave home or the hotel's charging station with 90-100% of charge and leave the superchargers with 80% (or less). For Houston-Dallas or Dallas-San Antonio, it'll probably be faster to stop at two superchargers and charge between 0-80 than to try topping off at one charger and skipping the second supercharger.

    Hopefully we'll get some route planning tools - on a website, mobile app or in the car (either from Tesla or a 3rd party) - that take a route, project energy usage, and provide advice on charging levels and charging stops... In addition to adding this route planning feature to the in-car navigation software, the nav software could also be monitoring energy usage and provide advanced warning when there was risk the car might not make it to the next supercharger and provide advice on slowing down to extend the range enough to make It safely to the charging station.

    The software for implementing these features shouldn't be too difficult to implement (the hard parts on navigation routing are already there) - and would help to further simplify the ownership experience in driving the car long distances...

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