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Near annual replacement of 12V battery is typical according to Tesla Service Tech

Discussion in 'Model S: Battery & Charging' started by ecarfan, Jan 15, 2015.

  1. JRP3

    JRP3 Hyperactive Member

    Aug 20, 2007
    Central New York
    DC/DC should power up when the 12V battery voltage drops to a specified level and keep the battery charged, just like a battery charger. If it doesn't I'd say there is a problem with the DC/DC converter.
  2. Cyclone

    Cyclone Cyclonic Member ((.oO))

    Jan 12, 2015
    Charlotte, NC
    Well that didn’t last long. My last 12v lasted almost four years. Since one got out in in early March and I already got the replace 12v message. Similar to last time, I noticed this week I had much higher vampire drain, but I figured it was because of the fall weather. Guess it was both.
  3. N..8

    N..8 Member

    Dec 20, 2017
    Sanford, NC
    If your getting a good amount of Vampire drain then your 12v is taking a beating. The HV pack doesn't just discharge on it's own, the contactors have to be engage to run the systems either 12v (13.2) or HV (350/400). If your car isn't going to sleep then the 12v systems are working hard on something and everytime that 12v gets to 12.4 or 12.5v then the DC/DC kicks in and supplies 13.2v from the HV battery. This is where the HV Vampire drain comes from on most normal cases. If your car is actively charging then the DC/DC contactors are closed and keeping the battery at 13.2v. I think some of the people here that drive lots of miles a day and charge from home will see long life in their 12v batteries. Due to driving keeps the battery at 13.2 and while charging for the 4 or 5 hours at night does the same. Cycling the Lead Acid battery so many times takes a toll on it. I use a NOCO Genius and my car will loose maybe 1% over 4 or 5 days if I have it parked in the garage. If my car isn't in sleep mode then the NOCO helps but a trickle charge doesn't make up for what the car uses. I haven't tried to put the NOCO on 13.6 supply mode yet and keeping the car awake but may give it a try for test run.
    • Informative x 3
  4. dabbler

    dabbler Member

    Nov 30, 2015
    Toledo, OH
    I have been going on my fourth year with out replacement of the 12V battery. I also charge from home on a regular basis (HPWC). Good to know that regular home charging extends the life of the 12V battery. I don't see any change in vampire drain over the years. I suspect that when replacement time comes, I will be doing this myself.
  5. Barry

    Barry Active Member

    Aug 9, 2013
    My first battery lasted 6 weeks. Second one, almost 3 1/2 years and still going.

    While I have no proof, I suspect that Tesla loosened up their 12V battery "early warning system," and doesn't flag weakening batteries as early as it used to.
    • Like x 1
  6. ohmman

    ohmman Maximum Plaid Member

    Feb 13, 2014
    North Bay, CA
    Replacing the 12V on my X today. 2.5 years old. My S is 4.5 years old and hasn’t had a replacement yet.
    • Informative x 1
  7. BrokerDon

    BrokerDon Member

    Aug 23, 2014
    Newport Coast, CA
    Another data point. We just returned from a 4 month trip out of the country with our 2015 P85D (40,000 miles) plugged into our HPWC charging at 60A. With our Tesla set to maintain 80% we didn't receive a "replace battery" warning and our range is almost identical after a couple of drives to < 10% charge then recharge overnight on our HPWC.


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