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12V battery trouble

Discussion in 'Roadster' started by zack, Mar 4, 2012.

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  1. zack

    zack Member

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    My girlfriend and I took my Roadster out for its first 2012 drive, and after eating some lovely ribs we returned to the car and it wouldn't unlock. I walked around to the driver's side to see if the antenna was simply not picking up signal, and I could hear the two beeps normally associated with unlocking but the car remained locked. Stella leaned and looked in her window and said there was an message on the screen saying that the 12V battery needed service. I unlocked the door manually using the keyhole under the door (second time I've had to do that, but no alarm this time), and the car started up okay and I got it back to it's charger. I have an appointment Wednesday (probably) with my ranger Anthony and hopefully he can attend to it then.
     
  2. markwj

    markwj Moderator, Asia Pacific

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    It is the little 12V battery near the front wheel. I've heard of a couple of other cases like this over the years.

    The battery is designed to keep 'emergency' things working in the event of a primary ESS failure. Things like hazard warning flashers, brake lights, alarm, etc.

    It costs around US$20, and they'll probably just swap you a new one.
     
  3. zack

    zack Member

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    There's a lithium substitute for those stupid gel cells. I wonder if it would be acceptable to replace it with one of those.
     
  4. Doug_G

    Doug_G Lead Moderator

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    My 12V battery just failed, about a week after my annual service. Fortunately my Ranger is due to come back anyway.

    The car appears to respond to the key fob if I first "wake the car up" by flipping the charge port door open and closed. Failing that I could use the Tattler to unlock the door. Better than using the emergency key slot.

    Seems to me these batteries have a limited lifetime; perhaps they should be replacing them on a schedule...
     
  5. vfx

    vfx Well-Known Member

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    This has happened before and this been suggested.
     
  6. garry753

    garry753 RoadsterS753 ModelS P1449

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    Yep - I just had mine replaced as well - same key fob symptoms.
     
  7. daniel

    daniel Active Member

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    Thanks for the heads-up. If my fob stops unlocking the door, I'll try flipping the charge-port door.
     
  8. Doug_G

    Doug_G Lead Moderator

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    When it happens you'll get a VDS message. It goes away in less than a minute, but recurs next time you try to access the car.
     
  9. daniel

    daniel Active Member

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    A message on the VDS that goes away quickly is not terribly useful if you cannot get into the car to read it! :crying:
     
  10. Doug_G

    Doug_G Lead Moderator

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    It says "12V Battery Service Required" in letters large enough to see through the rear window. And it happens every time you get into the car.
     
  11. garry753

    garry753 RoadsterS753 ModelS P1449

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    The only issue being that you have to know to look for the message when the key fails, which for me wasn't immediately obvious...mostly you're just thinking "why doesn't my key work - oh it's a problem with where I am in relation to the car."
     
  12. ipdamages

    ipdamages Roadster Sports 835 & 972

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    my car has been having this issue for a few weeks. my "fix" is to use the key fob to unlock the door, and then the door won't open. but then i wait about 10 seconds for the notice to come onto the screen ("12 volt battery system not working," or something like that). once that message comes onto the screen, then the door unlocks and i can get in.

    the other thing i have done is to just drive without the top and then i reach in and open it with the inside door handle. since i almost always park in secure areas (my garage at work or my garage at home), this is an option for me - at least with good weather.

    i'm scheduled to get this fixed in a week at the tesla LA.

    elie at al & ed's in west hollywood makes a system that puts the 12V power on a plug that allows you to charge it, but i didn't feel like i needed it so i didn't so it.
     
  13. vfx

    vfx Well-Known Member

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    1.5s don't have a 12V battery.
     
  14. markwj

    markwj Moderator, Asia Pacific

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    Yep, that is expected. The car tries to do the unlock from the little 12V battery. When it detects that is no giving enough power, it spins up the main ESS and it's 12V converter (the car wakes up, little coolant pump starts, etc) and puts that message on the VDS. From then on (for the next five minutes at least) the car will run from the ESS 12V converter and key fob should work. Opening the charge port door, or pressing a door handle, has the same affect.
     
  15. daniel

    daniel Active Member

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    So the car is awake and listening even if the 12-v. battery is dead? And when it hears a call to unlock the door, it can't, because the little battery is dead, but it can turn on a separate system to get power and do everything it's supposed to?

    In the Prius, if the 12-v. battery dies, you have to jump it before the car will do anything.

    Where is the Roadster getting power from to "listen" if it has no power to unlock the door??? If the main traction pack is alive and providing power to "listen" for the fob, what's the 12-v. battery even there for? And why can't it use that power to unlock the door?

    I guess a more concise question would be: I know that the car is monitoring its batteries all the time, whether on or off, and can run its cooling system even when the car is off. So what's the 12-v. battery for, and why is something as important as unlocking the door tied to a short-lived 12-v. battery rather than to the same system that's always on and monitoring the car?

    I'm confused.
     
  16. markwj

    markwj Moderator, Asia Pacific

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    The little 12V battery is there primarily as a safety system. Should the main ESS completely fail, while driving or on the road, it provides power to emergency systems - brake lights, hazard warning lights, doors, etc.
     
  17. Doug_G

    Doug_G Lead Moderator

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    ... and for some reason it also operates the door and trunk locks when main power is shut down.
     
  18. DrComputer

    DrComputer Member

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    It seems to only operate the drivers door. When my 12v battery failed you could still open the passenger's door remotely but not the driver's door.
     
  19. strider

    strider Active Member

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    That behavior is if the 12V battery is weak but not dead. If the battery is dead, you have to open the charge port door or use a Tattler/OVMS to "wake up" the car. Power will then run from the main traction battery through a 12V converter (transformer?) to allow you to open the doors.
     
  20. wiztecy

    wiztecy Active Member

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    The 1.5 roadsters use battery sheets 1 & 2 to supply power while the car is off.
     

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