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12 Volt Battery Saga

Discussion in 'Model S: Driving Dynamics' started by DoctorZ, May 21, 2016.

  1. DoctorZ

    DoctorZ Member

    Joined:
    May 11, 2016
    Messages:
    18
    Location:
    Afton, Virginia
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    About 8 weeks ago, an onscreen displayed message (warning) regarding my 12V battery showed up on my '13 P85+.
    I called the Tyson's (VA) service center; they kindly fit me in 48 hours later, suggesting this could not wait. The 12V was replaced, no charge, under warranty.

    Fast forward to yesterday....

    Long story short, we moved 5 weeks ago; the S remained garaged at previous address. I went to pick it up, move it to its new home. It had remained plugged in (110 for maintenance; the light on the cord glowed steady green.) I got zero response to any fob commands and Tesla app could not connect to the car. I called support who suggested I might need a new 2032 fob battery; an hour later, with fresh battery, still no response. Support suggested roadside should be dispatched, S flat bedded to Tyson's (where it was scheduled for its annual this Tuesday coming.) I would be responsible for 2+ hour tow fee! I asked if there was anything I could do. Tech got on the line and suggested I remove the nose cone and try to jump start. That did the trick :) I was able to drive it the 75 miles to new home and the new 12V seems to be holding its charge.
    The tech suspects some charging inadequacy or a problem with the battery itself; though unused, it seems like it should be able to hold a charge for 5 weeks(?)
     
  2. Snerruc

    Snerruc Member

    Joined:
    Apr 16, 2016
    Messages:
    227
    Location:
    Kailua kona
    It may be that the 12 volt wasn't getting charged in storage. On an ice car I always either pull a battery cable or put it on a trickle charger. Almost all modern cars have voltage leakage when off. Not sure how this is handled with Teslas, but I would research. Otherwise, it may happen again.
     
  3. Atebit

    Atebit Member

    Joined:
    Jan 7, 2014
    Messages:
    273
    Location:
    PA
    As long as it's plugged in (even to the UMC at 120V) the car will maintain the 12V battery. Last summer my S was in a garage for over 4 months at 50% SOC, connected to the UMC at 120V (and dialed back to 7A just to make sure everything stayed cool...it wasn't my garage). At the end of that time, the S booted back up fine, no issues with my now (at least) 26 month old 12V battery since.
     

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