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"Early" supercharging throttling: common problem?

Discussion in 'Model S: Battery & Charging' started by Moonwick, Aug 2, 2017.

  1. Moonwick

    Moonwick Member

    Joined:
    Dec 4, 2014
    Messages:
    72
    Location:
    Atlanta, GA
    Today on our way back from Florida I stopped at the Supercharger in Auburn, AL with my battery at 1% (was aiming for more of a buffer, but didn't anticipate a 12mph headwind!) and plugged in to stall 1B. The contactor kicked in, and within a moment I was happily charging away at 115kW. However, within the first 2 kWh the rate started to decrease dramatically, and about 5kWh in I was only charging at 70kW. I disconnected, shifted down the line to 2A, plugged in, and once again started out at 115kW, only this time at 4kWh in I was already down to 60-65kW... even worse than before! For the record, I was the only car at the station the entire time, so I wouldn't have been sharing a charger stack with another car.

    Third station I tried, 2B, worked perfectly, however. Sustained 115kW until the usual SoC taper point, and had no trouble at all with early taper.

    Auburn is one of the older stations (though the charging handles have been replaced at some point, since they do feature the new style of release button) and I've seen this same behavior on a recent trip at Louisville, Bowling Green, and even at the station in Brentwood, TN at the service center--all of which are older stations. I suspect that the contacts on the charging connectors are getting dirty, and that there needs to be some more regular maintenance taking place with these.

    On the same trip that took me through Louisville, Bowling Green and Brentwood, I also stopped at the new station in Athens, AL. The first (and only) station I plugged into also had no trouble with taper, presumably since it's still nice and new.

    So, anyone else noticing this? Is it time for me to start carrying contact cleaner and swabs with me on roadtrips? :eek:
     
  2. ChadS

    ChadS Petroleum is for sissies

    Joined:
    Jul 16, 2009
    Messages:
    2,571
    No, I haven't seen it.

    Dirty contacts may well be the case, but hot chargers or a hot car can cause that too. Maybe the first two chargers cooled your battery just enough for the third to charge faster? Or maybe they had been in use just before you arrived?

    It is always hard to tell what us going on as there are so many factors.
     
  3. chillaban

    chillaban Active Member

    Joined:
    May 5, 2016
    Messages:
    1,898
    Location:
    Bay Area
    I’ve seen this particularly at older sites, or in direct sunlight. My best theory is that the charging handle / cable is heating up which leads to charge rate tapering.
     
  4. Buster1

    Buster1 Member

    Joined:
    Oct 13, 2016
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    227
    Location:
    Las Vegas
    What did your cooling louvers do during this timeframe?
     
  5. Muzzman1

    Muzzman1 Member

    Joined:
    Feb 8, 2014
    Messages:
    278
    Location:
    Los Angeles
    I actually experienced the exact same thing on my car doing a weekend trip to Las Vegas
    Here's a graph of that exact scenario:


    Screen Shot 2017-08-03 at 9.52.49 AM.png
     
  6. Moonwick

    Moonwick Member

    Joined:
    Dec 4, 2014
    Messages:
    72
    Location:
    Atlanta, GA
    Hm, I don't really recall.
     

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