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12V Battery Replacement Cost

Discussion in 'Roadster' started by shrink, Jun 5, 2018.

  1. shrink

    shrink Supporting Member

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    The "SWP: Aux Battery Supply Low" ID: 428 message popped up on my VDS over the weekend. I found that pretty impressive considering I live in a desert and I've been on the same battery as when I bought the car as a CPO in 8/2013.

    Anyway, I'm about due for annual service so I just scheduled it all together.

    Annual Service: $600
    Auxiliary Battery: $250 :confused:

    That battery replacement costs seems a bit much. I complained, but my regular service advisor is out on paternity leave, and all the new faces didn't seem to care that much.

    Does this $250 12V replacement seem right to others. The price was handwritten on my service invoice and I got the sense they were just winging it.
     
  2. gregd

    gregd Active Member

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    Seems like a deal.

    Cost me $531.81 in Feb 2015, but that was a stand-alone repair (not combined with an annual service, if that matters). $131.81 for the battery itself, $400 for labor.
     
  3. Zhelko Dimic

    Zhelko Dimic Careful bull

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    I paid around $200 for a Porsche battery and $220 or so for a Merc one. On top of that I got charged at least 1/2hr which would be $70-$75 at current prices.
    This is at an independent shop, but good, expensive independent, ex master Porsche tech, though he never does work himself anymore...
     
  4. shrink

    shrink Supporting Member

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    Okay, that’s good feedback. I guess I was just used to dropping $80 at AutoZone or Costco and doing it myself in my former ICE cars.

    Unfortunately, I do not currently own a low profile jack to raise that wheel and pull off those wheel well panels.

    Actually, figure $100 for the battery + hour of shop labor and I guess that seems about right. Wish they’d just roll that labor cost into the annual service.

    Regardless, I can live with this.
     
  5. rudholm

    rudholm Member

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    My understanding is that they replace the 12V battery as part of the annual maintenance.
     
  6. Zhelko Dimic

    Zhelko Dimic Careful bull

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    Other manufacturers offer about 24 months of warranty on the battery. Not sure about Tesla but could be the same for the 12V. I just had mine replaced free of charge at 18 months by the ranger. Awesome experience, he even ventured and found my car himself into a sprawling multi-tier, multi-building underground parking garage at my work (the most complex parking structure I've ever seen in Toronto).
     
  7. MLAUTO

    MLAUTO Member

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    Thte batteries are less than $35 on eBay and you don't need a jack to change them. It only takes about 1/2 hour on the ground.
     
  8. gregd

    gregd Active Member

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    No, the only batteries replaced as part of the annual maintenance are the ones in the key fobs. The 12v battery should last many years, as it's not apparently cycled like the MS/X ones.

    During my replacement I asked the technician to install a short set of wires and a connector (all of which I provided) to bring access to the battery up into the accessible part of the car under the front hood. The idea was to allow me to "jump" the car if necessary, without needing to take half of the car apart to get at the battery itself. The side-effect of this connector is that I can monitor the voltage at the battery whenever I want, and interestingly, it stays extremely constant at 13.78 volts, whether the car is awake or asleep. So at least in my car, the battery is apparently being kept at a float charge level by an always-active DC-DC inverter somewhere within the ESS. (And, yes, I have a 2.0 car, not a 1.5!) Based on this, I expect the only time the battery would actually be used would be if the ESS or inverter failed, which should be rare.
     
  9. ShawnA

    ShawnA Member

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    Hi Shrink,

    The last time Tesla replaced the battery in my Roadster they charged:
    $131 for the 12V 8 Amp/hr battery
    $192 for the labor or $323 for the total job.
    That was in December 2013.

    I replaced the battery myself in November 2017 - Last November...

    I did it myself and I used a 12V 12 Amp/hr battery sold by Gruber on eBay for $57.
    I replaced it myself and I was happy to do it.
    It helped to remove some of the "mystery" surrounding the car.
    Like @gregd above I added a harness to the front grill where I can attach a Battery Tender
    trickle charger.

    Shawn
     
  10. shrink

    shrink Supporting Member

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    Good to know. Gruber is right here in Phoenix. I probably should have driven up there and picked up a battery. Oh well. Next time.
     
  11. gregd

    gregd Active Member

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    Hi Shawn,

    Does your battery stay at about 13.8v when the car is asleep? I thought this was odd, and the tech I talked to couldn't explain it. He thought the only the battery was powering stuff when asleep, so by his understanding it should have dropped to ~12.6v, and slowly dropped from there.

    Have you actually needed to put a battery tender on it?

    Greg
     
  12. Rolf68

    Rolf68 Member

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    France
    I changed the 12V battery myself 2 weeks ago.

    Costed 70 euros to buy a Lithium 12V battery, which is much lighter than the original lead one. No need to have a low jack to raise the car, you just have to roll the rear tyre on some wood planks so the car gets just high enough for a regular jack to acess the middle lift point. Then remove the left front wheel, open the access and replace the battery. Was quite easy and interesting thing to do :)

    Best regards
     
  13. ShawnA

    ShawnA Member

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    Hi Greg,

    I just checked my Roadster aux. battery and it was 13.7 Volts.
    My Roadster mechanic said that the battery only charges while the car is driven.
    I know we have heard differing stories about this...
    Since retirement the Roadster does not get driven as much as it used to...

    It may or may not need it but it is connected to the battery tender.
    I have created a "special" system for my 12 Volt powered equipment.
    Everything with a 12 Volt battery is connected to a battery tender.
    The outlets that feed the battery tenders are on a timer.
    The timer is "on" one hour per day.
    It keeps everything topped off and ready to go.
    It avoids boiling my batteries.
    They all say they won't overcharge, but one large boiled battery lost was too many for me.

    Shawn
     
  14. gregd

    gregd Active Member

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    #14 gregd, Jun 8, 2018
    Last edited: Jun 8, 2018
    Hi Shawn,

    If the battery is at 13.7 without the tender running, then the tender isn't needed. In fact, I'd be a little concerned about back-feeding the car's charging system from the tender. Unlikely it would be a problem, but certainly not necessary. Just keep the car plugged in, and it should take care of both the ESS and 12v systems by itself.

    I think the statement that 12v charging occurs only when the car is driven is wrong. My data, and now yours, confirms this. No 12v lead-acid battery is going to sit at 13.7 volts by itself, even without a load on it. Following the MS 12v battery threads, the Models S and X are apparently different. From what I've read, evidence is strong that they let the 12v battery power the car while it's asleep, then recharge it from the ESS when it gets low. Given the size of the MS/X 12v battery and the complexity of the car's systems, this cycling can occur several times per day, which fries the 12v battery in a few years or less. The very newest cars, and hopefully the Model 3 as well, seem to have gone back to our system, where there's a DC-DC system running all the time, to keep the 12v system happy, calm, and un-cycled.

    Thanks for the data,

    Greg
     
  15. ShawnA

    ShawnA Member

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    Hi Greg,

    The car is not at my house but at an outbuilding...
    The reading this afternoon at 13.7 could have come from last night's battery tender charge
    or this afternoon's ESS charge.

    To get a "real" data point for you, I will unplug the battery tender for a week and take another reading.

    Our ESS in Roadster taking care of themselves can and do go to Zero if not charged.

    I thought the "new" idea for the original S and X was to let the 12V take care of the ESS overhead.
    If it died, too bad, it was sacrificial, the ESS was protected from draining itself through its overhead.
    It seems to be working, BUT the loss of the 12V has become a problem itself.

    Shawn
     
  16. gregd

    gregd Active Member

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    Hi Shawn,

    No need to run it for a week. A 12v battery will drop back into the 12.x volts range within minutes of being pulled off the charger, so your reading a week from now will be no different.

    What Tesla learned, I think, with the MS/X 12v battery cycling was that a battery that cycles itself so often simply won't last. Nice in theory, bad in practice. With those models, the 12v system is powered by a DC-DC inverter from the ESS only when the car is on, so unless you're driving the car constantly, it's going to be cycling. From what I've read, the latest cars don't do that, and instead have a constant ESS-derived 12v system so long as the main ESS has sufficient power. Net, I think the resulting drain is going to be a wash, or even better since battery charging has some loss. The 12v battery in the new cars, as apparently in ours too, is only for emergency use (e.g. the hazard flashers) if everything else is dead.

    I understand the risk of simply leaving the car plugged in and otherwise forgotten. There have been several sad reports of power glitches and such that have confused the car, which subsequently drained and bricked the battery. If your car is left unattended for long periods, I'd strongly recommend getting an OVMS v3 module so you can keep an eye on it remotely. Besides enabling you to actively look at the car's status, the module will also send you any alerts the car might generate, including any low voltage alarms and even alerts that don't get displayed on the VDS. Very handy.
     
  17. ShawnA

    ShawnA Member

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    Hi Greg,

    I tested it overnight. The next day it was still 13.7 volts.

    Please remember my unique setup the (aux) battery only charges 1 hour per day with my timer.

    Also the Gruber replacement battery is 12 Amp/hr instead of the 8 Amp/hr standard battery.

    Shawn

    PS OVMS v3 on order and shipped. Anxious receive and install it.
     
  18. Tozz

    Tozz Active Member

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    I paid about 350 euro's for an Audi A6 battery. That is about 410 USD. The explanation behind this ridiculous pricing was that it the car needs to relearn/pair the battery or whatever bad excuse they had.
     
  19. gregd

    gregd Active Member

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    Hi Shawn,

    I really don't think your charger is doing anything. A fully charged 6-cell battery with lead-acid chemistry has a no-load resting voltage of 12.6 volts (Lead–acid battery - Wikipedia). That's chemistry. Anything higher than that must be externally induced. Since our batteries appear to have a resting voltage of 13.8 volts, it has to be coming from somewhere else (i.e. the DC-DC inverter inside the ESS). Given that the car is already providing the float voltage, your charger is unnecessary. I don't expect it's doing any harm, so if it gives you some peace of mind, have at it.

    Enjoy the OVMSv3! One warning - don't get concerned about what it tells you about the 12v battery voltage. It's not reading it at the battery itself, but upstream and on the other side of a lot of circuitry in the car.

    Greg
     
  20. rudholm

    rudholm Member

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    This kind of thing is why dealer service centers have a reputation for being frauds.
     

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