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12v battery issue explanation, sort of...

Discussion in 'Model S: Battery & Charging' started by jeffro01, May 8, 2013.

  1. jeffro01

    jeffro01 Active Member

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    Elon just said on the earnings call that the sudden rash of issues with the 12v was due to Tesla ordering from an American company who outsourced the production to a Chinese company who then outsourced the production to a Vietnamese company which led to a substandard battery. They have since discovered and addressed the issue.

    Interesting... Hopefully I'm not the last to know this LOL...

    Jeff
     
  2. andrewket

    andrewket 2014 S P85DL, 2016 X P90DL (soon 100)

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    He also said that they had improved their testing of the 12v battery. So an improved battery and improved testing that started "a few months ago."
     
  3. Cosmacelf

    Cosmacelf Active Member

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    I'll say it again. I think Tesla has made a major design error by relying on the tiny 12V battery to start the car. They have not designed in a backup to the 12V battery, so when the 12V battery dies, the car cannot be started and is in fact completely unresponsive. And has been proven with all the dead cars due to the faulty battery batch, owners have ZERO warning that their 12V battery is about to die. At least in an ICE, you can hear the starter battery struggling to start the car for a few weeks before it finally dies giving you some warning. Tesla could have created a simple backup DC-DC converter as a backup to the 12V battery. They could have eliminated the 12V battery entirely, and used two DC-DC converters. Or as a final backup, they could have exposed some 12V battery terminals so that the Tesla could get a boost from an ICE or external 12V battery for when the 12V battery dies.

    From where I'm standing right now, unless Tesla is willing to replace all owner's 12V batteries on an accelerated time schedule (like every two years), it is almost a guarantee that we will all have a dead model S at some point due to the 12V battery failing. It is just a matter of time.
     
  4. andrewket

    andrewket 2014 S P85DL, 2016 X P90DL (soon 100)

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    You don't want the traction battery always supplying current. The 12v system powers a relay that connects/disconnects the traction battery in the event of an accident. It fails open.

    I agree easier access to the jumping terminals would be nice, as well as a larger 12v battery.
     
  5. Johan

    Johan Took a TSLA bear test. Came back negative.

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    It's pretty easy to access the terminals. Just pop off the nose cone.

    It would have been cool if they had gone with a mini Li-ion 12V pack though... They could probably just have made a pack like that from a couple of the 18650 cells in both parallell and serial connection, and a simple controller...
     
  6. celter

    celter Member

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    I have a trickle charger that I use for my motorbike to keep the 12V battery fully charged all the time. Could this be a tempory solution to the Model S 12V problems, until they have found a permanently solution?
     
  7. JRP3

    JRP3 Hyperactive Member

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    If the batteries are faulty a charger won't help. Frankly since some of the replacement 12V have failed as well and since we've seen higher than recommended charge voltages reported from some people I'd say they also have a DC/DC converter problem. They do need a separate 12V battery to wake up the car after a long term shutdown, when they enable sleep mode again to stop the vampire drain. They should have made both the 12V battery and the terminals more easily accessible.
     
  8. SCW-Greg

    SCW-Greg Active Member

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    Indeed. Popping the nose cone off is not an attractive or intelligent solution (read kludgy) to something that may need to be addressed every 3 years or so. It's not something I want to do, and I'm comfortable taking things apart. Just seems too invasive.

    Further, does repeated attempts in taking nose cone off affect a secure fit? Does it become loose and sloppy if you remove too many times? Will any of the tabs break?
     
  9. FlasherZ

    FlasherZ Sig Model S + Sig Model X + Model 3 Resv

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    Safety standards require such an arrangement, such that high-voltage cables are not energized unless systems are normal.

    Applying 12V to the nosecone lugs will cause the car to close the contactor so that you can drive home absent of the 12v battery. Perhaps we just need better detection/diagnostics there.

    An alternative: As I understand it, the EV1 had a manual push-button which could close the contactor in case of a failure like this.
     
  10. ElSupreme

    ElSupreme Model S 03182

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    Do you think every other car made today has a 'major design error' because I know of no vehicle made today that doesn't rely on a 12V Pb-Acid battery to 'start'.

    I kind of like the fact it is a standard 12V Pb-Acid battery. It makes it really easy to jump or trickle charge.

    I think there is a major role for an 'accessory' battery in vehicles. A traction battery just isn't designed to run accessories. Best keep the jobs separate. Whether or not 12V or Pb-Acid is the why to go is definitely up for debate. But it is far from a 'design error'. More like a decision, that you dislike.

    EDIT: And I think you should be more worried about the CR2032 battery in the FOB that is relied upon to start the car. It is much more likely to fail.
     
  11. JRP3

    JRP3 Hyperactive Member

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    Except the traction pack is in fact running the accessories through the DC/DC converter, as well as charging the 12V battery.
    Obviously that has not been the case considering all the 12V failures.
     
  12. ElSupreme

    ElSupreme Model S 03182

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    You have to admit that charging a battery periodocially is a MUCH different use case than providing always on accessory power in a car. The traction pack just isn't desigened for such a duty. It can be done look at the 1.5 roadsters. But it must be challenging, Tesla went to a 12V Pb cell battery, Nissan and everyone else is doing the same with their car.

    A high voltage, high capacity, high variable demand, large battery pack isn't what you want running your background tasks 24/7.

    And I would contend that keyfob primary cell batteries are much more prone to failure than Pb acid batteries used to start cars. I burned through about 4 fob batteries in my VW and only one Pb acid starter battery.
     
  13. EarlyAdopter

    EarlyAdopter Active Member

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    Wouldn't you know it, a day after this revelation I get the "12v battery warning - service soon" error when I start the car this morning.

    One call to service and 90 minutes later they have a tech at my office to swap the battery. 30 minutes later I'm good to go. Amazing service.
     
  14. JRP3

    JRP3 Hyperactive Member

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    Fact is that's still what's happening. The 12V just makes it a fluctuating demand but the total energy transferred from the traction pack is the same. Actually higher because of the inefficiency loss of the discharge/charge cycle of the lead acid. So the 12V battery setup takes more energy from the traction pack than just running a DC/DC direct. The 12V is there because of the needed backup storage capacity that a DC/DC converter can't provide on it's own. What I'd like to see is a 12V lithium battery of the titanate variety, Altairnano or Toshiba Scib. Lighter and more durable than lead acid, no need for temperature management compared to the 18650's Tesla uses, just damn expensive at this time, but probably cheaper than Tesla having to keep replacing batteries. If they have their DC/DC problems fixed of course.
     
  15. William13

    William13 Member

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    Tesla is doing the conservative thing with a tried and true technology in tha lead acid battery. The warning light comes on and maybe needs to give a more drastic warning. I have only heard one report of someone unable to start or enter the car. The nosecone solution should work in a pinch.
     
  16. JRP3

    JRP3 Hyperactive Member

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    And screwing it up royally :wink: A car with 60 or 85kWh's of energy storage on board should never be stranded because of a faulty 12V battery. There should be a way for the car to jump itself at the very least.
     
  17. dsm363

    dsm363 Roadster + Sig Model S

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    With all the excellent engineering that seems to have gone into this car, is the 12V issue really an easy fix or was the perfect solution not done for cost reasons. Find it hard to believe they made such a design flaw when everything else seems on track (missing software features being added over time excluded).
     
  18. arg

    arg Member

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    One of the key issues here is fixing the 'vampire load'. With the vampire load as it is now, the 12V battery is being cycled quite heavily - reduce it and the 12V will probably last much longer (irrespective of whether they are currently lasting as long as they ought to).

    Reduced vampire load would also improve the one glaring user experience issue that currently exists with the 12V system even when everything is working as designed: having run the main pack down to 'empty', you need the 12V available so that you can release the parking brake to recover car and/or get it to start charging. Even the user guide warns you that you might need a jump start in this situation - and there have been a few reports on TMC and elsewhere of people who have run to empty and then had the 12V go flat before they could arrange recovery/charging and so needed a jump start. With properly minimised vampire load, the 12V should last months, though I am not sure if they can get it that low by software changes alone.
     
  19. William13

    William13 Member

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    As I understand it, the lead battery is better in theory at handling frequent deep current demands that would harm Li batteries. Of course they have used too small of a lead battery and have quality issues with the lead battery that are exacerbated by the vampire load. Likely they never did quality checks on the lead battery. The converters would burn out trying to supply the initial demand loads of the heat pumps etc.
     
  20. Al Sherman

    Al Sherman It's about THIS car.

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    In the meantime (and at the very least) those of us who are not handy at all, and in my case somewhat daunted, should absolutely get a "hands on" lesson on removing the nose cone and jumping the 12 volt. If I had seen it/done it once, I could have (most likely) avoided the towing fiasco that ensued when my initial 12 volt went tango uniform.
     

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