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Extended 12 V Battery Maintenance

Discussion in 'Model S: Battery & Charging' started by Sharkbait, Jan 21, 2017.

  1. Sharkbait

    Sharkbait Member

    Joined:
    Apr 5, 2016
    Messages:
    477
    Location:
    Los Angeles
    I've read various threads of how to maintain the 12V battery while my Sept. 2016 S75 sits idle for about seven weeks. Recommendations include trickle chargers and just keeping the car plugged in seem to be common. I'm led to believe the 12V battery takes its power from the main batteries that power the electric motor. If true, can I simply leave it plugged in and set the charge for 70%? I assume the 12V battery will then take whatever it needs, whenever it needs it. Is it more complicated than that? Thanks in advance.
     
  2. Andyw2100

    Andyw2100 Supporting Member

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    6,564
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    Ithaca, NY
    I believe the plan you laid out should be fine. I might adjust it, though, to charge to 50%. Seven weeks is a pretty long time, and in general, the closer to 50% the better as far as your battery is concerned. You can charge it more when you return, or, if you need the range immediately, use the app to change to the higher SOC level the day before you return home.
     
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  3. brkaus

    brkaus Active Member

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    Jul 8, 2014
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    2,133
    Yes, you can (should) do exactly as you plan. The car will turn on the DC2DC converter every once in a while to recharge the 12V. The 12V will drain slowly due to the computers, cellular, etc (otherwise known as the vampire drain).

    If you want to go above and beyond, you *may* connect a trickle charger to the 12v. Totally unnecessary for function. But it will keep the DC2DC from turning on as frequently.
     
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  4. Larry Hutchinson

    Joined:
    Dec 15, 2012
    Messages:
    108
    Location:
    Beaverton, OR
    Your car is new enough to have virtually zero vampire drain if you have energy savings on and, optionaly always connected off.

    As I have reported elsewhere, I had only one mile loss over 2.5 weeks. (If memory serves.) With always connected on, I lost a bit under one mile per day over the same time period.
     
    • Like x 1
  5. Sharkbait

    Sharkbait Member

    Joined:
    Apr 5, 2016
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    477
    Location:
    Los Angeles
    Right. I was told by another owner to turn on energy savings. Thanks for all the replies.
     

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