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12 volt battery dead

Discussion in 'Model S: Battery & Charging' started by mikeg561, Jul 10, 2015.

  1. mikeg561

    mikeg561 Member

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    Today marks my 2 week anniversary of having my car. Go out to the garage this AM and there is a warning message. "Car needs Service" "12 volt batter low"

    Car will not go into gear. Call service and they are bringing me a loaner car and a flatbed truck to take the car into the shop.

    Based on searching this forum, I thought the 12 volt battery issues were behind Tesla.

    Anyone else having this issue lately?

    Now I need to see how long I will be without my baby. :-(

    Mike
     
  2. mknox

    mknox Well-Known Member

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    I have never had a 12v issue, but Tesla has at least twice now proactively replaced my 12v battery at various servicing intervals.
     
  3. Barry

    Barry Member

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    I had the "12v battery low" warning after about 2 months of ownership (last month) and 2000 miles. Due to a backlog at the Denver SC, they gave me an appointment 4 weeks out for replacement and assured me the car would be fine in the meantime. They were right - it never died on me.
     
  4. martinwinlow

    martinwinlow Member

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    I am wondering if this issue is in any way related to whether or not people leave their MS' plugged into the mains permanently whilst not driving. Has a poll on this been done yet?

    Q "If your MS has suffered a 12V auxilliary battery failure, do you park your MS with a live mains connection; a/ always, b/ mostly, c/ half the time, d/ not much or e/ I only use SuCs to charge."...?

    I understand that the MS will charge the auxiliary battery from the main pack when it gets low if left disconnected from the mains long enough. Is this extra cycling to blame for premature auxiliary battery failures or is it just poor auxiliary battery manufacturer quality-control?

    I was mildly surprised to see that the auxiliary battery is only about 35Ah - same size as my i-MiEV. MW
     
  5. Barry

    Barry Member

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    When I'm home, I'm always plugged it. When I'm out during the day, I'm not plugged in while parked. I haven't taken the car on any overnight trips, so it's been plugged in every night.
    IIRC, I was away on a 4 day trip (without the car), and when I came home, I saw the low battery warning message.
     
  6. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

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    My speculation is that Tesla purchases these batteries in very large quantities to get a price break and some of them sit too long before being installed.
     
  7. martinwinlow

    martinwinlow Member

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    Left plugged in? MW
     
  8. apacheguy

    apacheguy Sig 255, VIN 320

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    OP - Can you please post back with Tesla's disagnosis? I strongly suspect the 12 V was not the root cause.
     
  9. Lex

    Lex Member

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    In another thread it is suggested that the Model S uses the 12V 1000x more than an ICE vehicle. This just might be a "consumable" to add to the cost calculator once the warranty is gone as there doesn't seem to be any easy alternative / replacement to lead acid.

    It's also a single point of failure that scares me, eg. may just need to push / pull if dead, and need to access the controls so I've put a backup battery jump-start pack (that also is has an air pump) in my trunk. Yep it adds weight but I think we have a real engineering dilemma on our hands here for the Tesla team as they plan the mass production model.
     
  10. mikeg561

    mikeg561 Member

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    Good thoughts from everyone. I will post the final results when I get them. I talked to service this AM, and they said they are replacing the entire battery pack. Did not get any more info yet. i.e. what really failed, what caused the failure, is the 12 volt also dead?

    FWIW, when home, I always plug the car in. I have not taken any long trips yet.

    Mike
     
  11. AndY1

    AndY1 Member

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    Replacing all these 12V batteries every year or so on every Model S is very enviromentally friendly.
     
  12. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

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    Batteries are the most recycled products and have been recycled for the longest time (I recall that they were recycled in the 1950s). In addition, they are almost 100% recyclable. I don't see a problem here in terms of environmental friendliness.
     
  13. Cottonwood

    Cottonwood Roadster#433, Model S#S37

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    I agree. Here is a good reference: Lead Acid Battery Recycling - Battery Council International
     
  14. Barry

    Barry Member

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    My speculation is it's a design flaw. Either the 12V battery is too small and/or being cycled too much, or there are issues with their charging algorithm that's killing them early. This has been going on for too long to be one huge batch of bad batteries. Tesla doesn't have the cash flow position to buy years-worth of batteries for inventory.

    I wonder why they just didn't build a Lithium-based 12V battery pack. Cost?

    Yes. Tesla says keep it plugged in when not in use. You seem surprised...
     
  15. Cottonwood

    Cottonwood Roadster#433, Model S#S37

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    The problem is that the batteries are being cycled too much.

    This is caused by the excessive thirst of the Vampire, called the control circuitry that stays powered up even when the car is "off." The control circuitry design draws about 1kWh (3 rated miles) per day or about 42 Watts, even with the most power conserving settings. The lead acid battery 100% capacity is 12V*35Ah or 420 Wh. This means the lead acid battery is cycled about 2.5 times its capacity per day. Even the best deep cycle batteries are only good for about 1,000 cycles, or about 400 days. That is about how long the lead acid batteries last on average in a Tesla Model S.

    To solve this problem, Tesla needs to reduce the power draw of the "off" control circuitry, increase the capacity of the lead acid battery, or go to a battery chemistry with more cycles available.
     
  16. sorka

    sorka Active Member

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    The when is about 6 times day. The systems, with more recent software, unless they've fixed it, draw about 100 watts of power continuously. Was about 70 watts but it jumped a few updates ago. It's like having 3 hid headlights on continuously. Lead acid batteries were not designed to be discharged over and over again. They're meant to stay charged.
     
  17. kuttakamina

    kuttakamina Member

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    The newest Model S's use gel based batteries. (Atleast thats what I was told)
     
  18. Cottonwood

    Cottonwood Roadster#433, Model S#S37

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    Gelled-electrolyte, lead-acid batteries are less expensive than absorbed glass mat (AGM), lead-acid batteries, and it looks like they will have a little longer life in this application.

    See Gel vs. AGM vs. Wet Cell Batteries | Solarcraft for some info on the various types of lead-acid batteries.

    To really solve this problem, Tesla needs to greatly reduce the the power draw of the "vehicle-off" control circuitry.
     
  19. Barry

    Barry Member

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    This agrees with my previous comment about it being a design flaw - the 12V system is under-engineered for its demand requirements, as it currently exists.
    It still doesn't explain why some recent batteries (like mine) in new cars, needed to be replaced after 6 weeks/1500 miles.
     
  20. mikeg561

    mikeg561 Member

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    Tesla chose to swap out the entire battery pack. There was an intermitted problem with one of the connector among the 7,000 batteries.
    They picked up my car Friday about 10:30 am. Diagnosed and had a new battery pack in the car (based on looking at android app) around 4:00 pm Saturday. That included time needed to get a new pack sent from Fremont to Costa Mesa. Should get me car back on Monday.

    I guess the 12v was not the issue in this case.
     

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