TMC is an independent, primarily volunteer organization that relies on ad revenue to cover its operating costs. Please consider whitelisting TMC on your ad blocker and becoming a Supporting Member. For more info: Support TMC
Start a Discussionhttps://teslamotorsclub.com/tmc/tags/

12V battery failing after 8 months and 2200 miles since new

Discussion in 'Model S: Battery & Charging' started by rmnelson, May 15, 2017.

  1. rmnelson

    rmnelson Member

    Joined:
    Sep 11, 2016
    Messages:
    5
    Location:
    Eugene, OR
    Refreshed facia S60D delivered 9/17/16. Kept in a heated garage. Always plugged in when garaged. It has never overnighted without being plugged in. Updated to 75D a month ago. Last night I couldn't summon the car out of the garage, and when I got in the 12V warning was on. I understood that after some trouble in 2013 these issues were under control. Now I've got a 220 mile round trip drive to get a replacement. (Not complaining about the drive, I knew where the service center was when I bought the car.) I haven't seen reports after this short a period of time. Is this normal?
     
    • Informative x 2
  2. MP3Mike

    MP3Mike Active Member

    Joined:
    Feb 1, 2016
    Messages:
    3,639
    Location:
    Oregon
    I don't think it is normal, but I also think it is not normal for a Tesla to be driven that little.

    Just sitting is hard on the lead acid batteries, and worse in a Tesla because of the larger "vampire" drain.
     
  3. RayW

    RayW Member

    Joined:
    Nov 9, 2016
    Messages:
    164
    Location:
    Cypress
    I've heard of this problem while damaged Teslas sit at body shops 8-wks awaiting parts, but not when plugged in. Is that covered under warranty?
     
  4. Max*

    Max* Not Banned

    Joined:
    Apr 8, 2015
    Messages:
    6,310
    Location:
    NoVa
    12V's are covered under warranty.
     
    • Informative x 2
  5. RayW

    RayW Member

    Joined:
    Nov 9, 2016
    Messages:
    164
    Location:
    Cypress
    It seems like Tesla should send a mobile service van or flatbed to take care of the 12V battery.
     
  6. AnxietyRanger

    AnxietyRanger Well-Known Member

    Joined:
    Aug 22, 2014
    Messages:
    7,525
    Location:
    EU
    I think it is fairly normal for Teslas to get 12V battery replacements almost annually... it is definitely not rare.

    I don't get the point about "just sitting". Sure in an ICE sitting drains the battery, but in a Tesla that is plugged in, the DC will charge the 12V all the time... as it would driving around...

    I'd say real reason is Tesla's are really hard on 12V batteries. In ICEs 12V batteries last years and years, in a Tesla not so much.
     
    • Informative x 1
    • Like x 1
  7. MP3Mike

    MP3Mike Active Member

    Joined:
    Feb 1, 2016
    Messages:
    3,639
    Location:
    Oregon
    No it doesn't charge the 12v battery "all the time". While it is not charging the HV battery it runs on the 12v battery until it gets low at which point it closes the contactors, turns on the DC-DC convertor and recharges the 12v battery. (As far as I know the shore power only gets used when it is actually charging the HV battery, or you are pre-heating/cooling the car, so if you charge the battery to 90% and set the charge level to 50% it would be many days/weeks before the shore power was used at all.) Depending on your settings, and other app/services used, it can run full cycles on the battery multiple times a day. (Especially if you have something polling your car that prevents it from going to deep sleep.) And you only get so many cycles out of those batteries. (Of course it could have just been a defective battery to start with.)
     
  8. SSonnentag

    SSonnentag Member

    Joined:
    Apr 11, 2017
    Messages:
    18
    Location:
    Peeples Valley, Arizona
    I still don't understand why an EV, with all that battery pack available, still relies on a separate 12V battery.
     
  9. nwdiver

    nwdiver Active Member

    Joined:
    Feb 17, 2013
    Messages:
    3,212
    Location:
    United States
    Yep... that's the design flaw that Tesla needs to fix. It's not unusual for these poor little batteries to get cycled 5 times a day. That's absurd. Even a lithium battery is going to get beat to crap with that kind of use. Annual replacement of a battery is unacceptable...

    Using off-the-shelf components is critical to keeping costs down... most of the auxiliary components like the seat heaters, windows and computers need to run on 12v. What Tesla needs is a better DC-DC converter that can keep the battery on a float instead of cycling the crap out of it...
     
    • Like x 1
  10. MP3Mike

    MP3Mike Active Member

    Joined:
    Feb 1, 2016
    Messages:
    3,639
    Location:
    Oregon
    Because you have to have a way to turn off/isolate the HV battery. And once you do that you need power from somewhere to go through all of the safety checks before you can turn it back on. There are ways around it but some of them cause HV battery balancing issues, and others cost more. I assume Tesla figured that this way was the best solution at the time. Maybe the Model 3 will be different. (I think they went both with and without a 12v battery in the different Roadster versions.)
     
    • Informative x 1
    • Like x 1
  11. SSonnentag

    SSonnentag Member

    Joined:
    Apr 11, 2017
    Messages:
    18
    Location:
    Peeples Valley, Arizona
    I wonder if they have experimented with using a capacitor in place of the 12V battery. They're light and foolproof.
     
  12. MP3Mike

    MP3Mike Active Member

    Joined:
    Feb 1, 2016
    Messages:
    3,639
    Location:
    Oregon
    But how long could one run the MCU, door locks, etc.? And would it have enough power to close the contactors?
     
  13. Lloyd

    Lloyd Well-Known Member

    Joined:
    Jan 12, 2011
    Messages:
    5,331
    Location:
    San Luis Obispo, CA
    I had a replacement at 6 months. The 2nd battery is now 3 years 4 months.
     
    • Informative x 1
  14. stopcrazypp

    stopcrazypp Well-Known Member

    Joined:
    Dec 8, 2007
    Messages:
    9,188
    I don't think the DC-DC converter is the solution. It doesn't make sense to keep the HV pack energized the whole time the car is parked (is there any other EV that does this? plugged in and not charging or unplugged?).

    At the very least an AC-DC battery tender when the car stops charging (some people are doing this themselves manually). Reducing the amount of power the computers use is actually the core problem.
     
  15. Sully's8

    Sully's8 Member

    Joined:
    Jan 4, 2017
    Messages:
    155
    Location:
    Metro Chicago
    Actually a fairly common scenario. My 12v warning came on at 500 miles and 3 weeks. . .replaced under warranty about two weeks later due to schedule issues and travel. They were clear that the warning comes on several weeks before it's critical.

    The replacement took about 40 minutes and I was gone.

    No worries.
     
  16. RayW

    RayW Member

    Joined:
    Nov 9, 2016
    Messages:
    164
    Location:
    Cypress
    I believe they also use the 12V battery to heat the Li-ION battery pack when cold and also keep the MCU, doors, windows, etc. alive if the battery pack does drop to zero. The Li-ION voltage drops significantly when cold and need to be heated.
     
    • Funny x 1
  17. nwdiver

    nwdiver Active Member

    Joined:
    Feb 17, 2013
    Messages:
    3,212
    Location:
    United States
    The pack heater is ~10kW ~probably not ;)
     
    • Informative x 1
    • Funny x 1
  18. AnxietyRanger

    AnxietyRanger Well-Known Member

    Joined:
    Aug 22, 2014
    Messages:
    7,525
    Location:
    EU
    You missed my point.

    My point was: 12V batteries get charged on Teslas even while parked. (And being on shore power the car was not energy saving/constrained either.)

    So the presented point about the car just sitting there being hard for 12V battery makes little sense as these are not ICEs that only charge while driving.

    Now, the point about the charge cycles being hard on the 12V battery, that is very plausible - but nothing to do with remaining parked... As I said, Tesla's are hard on 12V batteries.
     
  19. nwdiver

    nwdiver Active Member

    Joined:
    Feb 17, 2013
    Messages:
    3,212
    Location:
    United States
    Well... it's got a little to do with being parked... if the car is 'on' then the HV contactor is closed and the 12v battery voltage will be maintained. It's when the car is 'off' and the HV contactor is open that the 12v battery gets cycled by vampire loads. So connecting a battery tender directly to the 12v battery if the car will be parked for long periods of time can likely spare dozens or even hundreds of cycles and greatly extend the life of the 12v battery.
     
    • Informative x 1
    • Like x 1
  20. Canuck

    Canuck Well-Known Member

    Joined:
    Nov 30, 2013
    Messages:
    5,109
    Location:
    South Surrey, BC
    I had to have the 12 volt batteries replaced in both my Leaf and Tesla far sooner than in any ICE -- about 1/2 the life span I expected of 4 to 5 years, which is my experience with ICE vehicles. Whether they will last 4 - 5 years this time remains to be seen.
     

Share This Page