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Ambient heat effect on charge rate

Discussion in 'Model S: Battery & Charging' started by Plug Me In, May 30, 2013.

  1. Plug Me In

    Plug Me In Member

    Nov 29, 2012
    Central Virginia
    Just had a first time occurrence for me today that I haven't read about before. I got back from a road trip today with about 50 miles of rated range left. I plugged into my 14-50 outdoors in the driveway. About 2 hours later, I need to run an errand and use the app to cool down the car, I notice it's charging at 27A / 22 miles/hr and the car won't let me increase the current. This was our first 90 degree day today and my driveway is sun exposed; really bakes in the afternoon. The outlet, plug and UMC brick are extremely hot to touch. I unplug the whole shebang and put it in a shady spot and go about my business. The driveway is a slight bit cooler when I get home, but for good measure I put a towel over the outlet to keep the sun off, and yes I did consider the odds that the towel would combust and I considered that very low. Charging started at 40A and was fine. Just for reference the UMC was extremely hot but I could handle it to unplug it. Not as hot as the door handles get in the sun.

    I'm assuming the car limited the current due to the excessive heat. It generally won't be an issue for me as I do most of my charging at night but I may need to keep the cable somewhere cooler during the day as it probably isn't good for it to bake everyday like that. Other option is to fashion some kind of roof or shade for the outlet. Opinions?
  2. DriverOne

    DriverOne Supporting Member

    Aug 20, 2012
    Austin, TX
    The Supercharger FAQ talks about slower charging speed in temperatures over about 100°F. So likely this is similar to what you are seeing.

    My charger (10-40) is shaded in a garage, yet the 10-40 adapter and cabling gets hot, with an ambient temp in the 80s and getting hotter as the summer comes on! I've manually dialed the amperage down in an attempt to lower the adapter heat. I'm glad to hear the car will do it automatically.
  3. Todd Burch

    Todd Burch Voltage makes me tingle.

    Nov 3, 2009
    Smithfield, VA
    This was almost certainly not because the charge cord/plug/outlet were hot, but because the battery pack itself was hot. Charge rate was limited because either a) some of your charge energy was going into chilling the pack to the desired temperature for charging, b) charging current was limited to prevent damage to charging a warm pack, or c) both.
  4. jomo25

    jomo25 Active Member

    Mar 16, 2012
    Scottsdale, AZ
    The Roadster EVSE would shut down/trip when ambient temps approached 115, esp. if sitting in the sun. My ROadster owning friend said that when the brick surface temp exceeded 150 it would stop working. Maybe the reduction is their means to keep it from stopping altogehter. Im in PHX, but I only charge in an underground garage (and then with a J1772 station). So, I cant speak to if your experience is normal. Also, note that the battery mgmt system may need to work harder in extreme high temps, (to keep the battery in a cool safe range while applying high current). Thus the net amount of charge you get may be reduced in high ambient temps. But I'm not sure about the reduced current.
  5. strider

    strider Active Member

    Oct 20, 2010
    NE Oklahoma
  6. ZBB

    ZBB Emperor

    Feb 27, 2013
    I'm also on PHX, although in the foothills in far north Scottsdale -- so temps normally peak ~6 degrees lower than downtown. But our garage is on the SW corner of the house -- so it can easily be from 90-110 in the garage a good portion of the summer. I get my car this week, so will be interesting to see how it handles the hot garage...
  7. Stimyg

    Stimyg Member

    Feb 17, 2013
    New York
    I think I had the same issue today. 90 or so, sunny, car throttled the usual 40amps down to about 32.

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