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12 Volt Battery Saga

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

  1. DoctorZ

    DoctorZ Member

    May 11, 2016
    Afton, Virginia
    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

    Apr 16, 2016
    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

    Jan 7, 2014
    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 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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