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12v battery issue, Tesla horrific response

Discussion in 'Model 3' started by Tjhappel, Sep 19, 2020.

  1. brkaus

    brkaus Well-Known Member

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    Our Model 3 battery died yesterday. Left my wife stranded.

    Opened the app, requested service. They texted back in about 10 minutes. A few text exchanges and a tow truck arrived about 30 min later. Should have been quicker but they sent him to the wrong street.

    Tow guy was very familiar, boosted the battery and put it on the truck. I had already opened the frunk, but didn't want to put the booster on it because of strong sulfur smell.

    Now we see what happens today if service calls and if they have a battery in stock.
     
  2. scottf200

    scottf200 Active Member

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    Well I had a hard self-rule about that for 5 years and relaxed it that night after seeing 1000s successfully doing it. The key point is the DC-DC converter is shutdown during parts of the OTA so the 12v is on-its-own! If it the OTA was big (multiple sources say this one was) and/or the 12v battery was 'weak' then you could be in trouble.

    My thread (I monitored the 12v battery voltage during an OTA update) shows the graphics of monitoring an OTA (2020.40.4) after I got home and was in the garage with my new battery installed. It also refers to an article about deep cycle battery proper care and it seems Tesla *is* treating the 12v very well (voltage recharging/~14v and maintaining/~13v). My 48 hour graphic of the Tesla voltage management shows this.

    From article and quote below: Marine Battery Maintenance 101 - e Marine Systems
    *** "taken to 14.2-14.4 VDC before it is fully charged"
    *** "Once fully charged, marine batteries should be held at a considerably lower voltage to maintain their charge - typically 13.2 to 13.4 volts."
     
    • Informative x 2
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  3. sdrevik

    sdrevik Member

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  4. brkaus

    brkaus Well-Known Member

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    There is a thread here somewhere. A recent firmware update made the car complain about the ohmu battery. My theory is they were trying to improve detection of battery problems and the ohmsu responds a bit differently so it got flagged. Others believe Tesla is trying to stop aftermarket batteries (but I see no real reason for that - they are not a big profit item).
     
  5. lUtriaNt

    lUtriaNt Member

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    Ohmmu Battery & 2020.28.6 update

     
    • Helpful x 2
  6. hokiefan

    hokiefan Member

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    Add me to this list of dead batteries. 25k miles, Sept 2018 delivery. Model 3 dual motor. Called service and they wanted to tow it to the service center, no mobile appts available. Going to call the service center tomorrow and see if I can just pick up the battery and replace myself. It will be a major pain to have it towed, sit at the service center, and then have to go retrieve it (they won't tow it back).

    Glad it was in my garage because two hours prior I was at a shopping center with no other way to get home. With an ICE you can usually tell when the battery is going with slow cranking during start or dim lights. I can't believe they don't trickle charge the battery from the mains.
     
  7. scottf200

    scottf200 Active Member

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    I'm sure there are a lot of videos on the TM3 batter replacement. Likely similar to the TMX. a) Undo neg 12v battery post. b) do the disconnect (under rear seat in TM3), c) replace battery. d) connect main, e) replace 12v battery.

    Certainly they can't trickle charge because they need to disconnect the HV/HighVoltage battery for safety/regs.
     
  8. AlanSubie4Life

    AlanSubie4Life Efficiency Obsessed Member

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    I suppose you could leave Sentry on all the time when you're plugged in at home. Might get a bit old, though, and I'm not convinced it will actually solve any problem. Bad batteries are gonna go bad. It's not like they don't charge it. Leaving Sentry on all the time I suppose will reduce contactor wear, and possibly reduce the net energy actually drawn from the battery itself.

    But the expense would be large. 5kWh a day. Could pay for a new battery in 4 months (it's $120 for the Model 3 (possibly non-AGM) battery) at a relatively low CA electric rate of 20 cents/kWh.

    Contactors are also probably not too expensive but having them replaced probably is. Personally I'm hoping they are rated for 100k cycles.

    Also adding a lot of up-time to your DC-DC and all the other electronics in the car. Might not be a good idea.
     
  9. hokiefan

    hokiefan Member

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    I got the battery out. Tried to charge it with my battery charger but it didn't take much charge. Tried reinstalling and was able to get the door open but then the driver window was starting to do funny things so I disconnected. Was reading 9.6v under load and 12.5v once I disconnected. Hopefully they have a battery I can go pickup tomorrow.
     
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  10. brkaus

    brkaus Well-Known Member

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    @hokiefan picked my 3 up today. They said battery was reading 8v under load. All better now.
     
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  11. AlanSubie4Life

    AlanSubie4Life Efficiency Obsessed Member

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  12. Austindude

    Austindude Member

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    Though I am still in warranty I went ahead and just replaced the 12V battery on my 2 & 1/2 year old 2018 Model 3 before it died. I scheduled with Tesla and they came to the house and took care of it. I also had them change the cabin filter and something else. I think I remember the battery and install was about $190 so I could have saved at least $100 by doing it myself but.... Anyway after hearing how much people are spending on all their Model 3 upgrades seems like proactively having Tesla replace the 12V is a no brainer.
     
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  13. lUtriaNt

    lUtriaNt Member

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    i also proactively replaced the stock battery with ohmmu battery 1 month after i bought the car. i keep the lead battery charged up monthly --just never know if ill need it for something...
     
  14. iwannam3

    iwannam3 Member

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    O'reilly auto parts shows the 51R AGM at $199.99. You sure about the $190 parts and labor and able to find an AGM battery for $90?
     
  15. Daniel in SD

    Daniel in SD Well-Known Member

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    I sort of doubt the Tesla battery is AGM, the manufacturer does not list it as an AGM battery. And as you point out, it's too cheap.
     
  16. scottf200

    scottf200 Active Member

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    This post on TOO brings it to question too (er ... as well).

    The 12 Volt battery in the Model 3, not AGM? - Tesla Owners Online
    Via: TOO member 'android04'

    [​IMG]
     
  17. Daniel in SD

    Daniel in SD Well-Known Member

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    Also half a dozen pages back in this thread.:p
    And if you think about it the AGM batteries were a fix for the original Model S 12V system design flaw, they originally shipped with flooded batteries. Eliminating that extra cost would make sense.
     
  18. brkaus

    brkaus Well-Known Member

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    I don't recall what the top looked like. Are there vent covers that can be opened to look at the top of the plates (if any)? I'll look at mine this weekend.
     
  19. Austindude

    Austindude Member

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    Well I just now went and pulled the paperwork from the glove box and you are correct the 12V battery replacement was not $199, it was $124! Maybe I was given some credit for the battery still being under warranty? Anyway I would have been happy to pay $199 just for the peace of mind of not being stuck somewhere. I'll replace it again when it gets closer to two years on the new battery.
     
  20. AlanSubie4Life

    AlanSubie4Life Efficiency Obsessed Member

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    No, no vents to open. There is a vent tube though.
     

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