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Tesla Roadster Battery Care

Discussion in 'Roadster' started by Palpatine, Mar 2, 2010.

  1. Palpatine

    Palpatine Banned

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    #1 Palpatine, Mar 2, 2010
    Last edited: Mar 2, 2010
    I sent some questions to Tesla Motors asking about strategies for extending the life of my battery pack. I was looking for more tips beyond just plugging in and recharging to standard mode each day.

    I received a very detailed response from Dan Myggen and he gave me permission to post it here.

     
  2. Palpatine

    Palpatine Banned

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    #2 Palpatine, Mar 2, 2010
    Last edited: Mar 2, 2010
    This is what I have started doing based on my research and talking with Tesla Motors.

    I set my Tesla to recharge at 6 am so that it finishes and balances right before I leave the house each day. That way my car spends more of it's time during a 24 hour day significantly below full standard. It is only briefly at that 87% charge level each day. The goal should be for the car to finish charging and balancing about 30 minutes before you leave in the morning.

    If you plug your car in each night when you get home (perhaps 6 pm) then it is likely topped off quickly and then spends all night at the full standard charge level. This is not a good thing. We want to minimize the amount of time the cells are fully charged.

    If I know I am not going to be driving my Tesla for a few days, then I will just leave it in standard mode at something less than full standard. I am fine with allowing it to get down to 90-150 ideal miles without recharging.
     
  3. Tdave

    Tdave Member

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    Thanks James. Fascinating. Sounds like 90% SOC Standard mode is pretty safe for the battery. So in other words, using Standard Mode and just plugging it in whenever is a pretty good strategy. And it happens to be the default for most people. That's good news.

    I'd be interested to know just how much better your strategy is compared with the mindless strategy I stated above. In other words, what's the difference in pack life?
     
  4. Palpatine

    Palpatine Banned

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    I read a study about these laptop batteries that quoted the loss of capacity per year when kept at certain temperatures and charge levels.

    When kept fully charged at 40 degrees celcius then the loss in capacity approaches 15% to 20% per year.

    When kept closer to 50% SOC and at 25 degrees celcius then the loss in capacity is about 4% per year.

    When kept at 50% SOC and 10 degrees celcius then the loss in capacity is about 2% per year.

    If I recall, Tesla states that they expect the average user to be at 65% of their original capacity after 100,000 miles. I am hoping that my strategy keeps my battery pack with much higher capacity over time.

    It is an easy change to make. Just select a specific time in the morning for the charging process to start. 5 am is likely a good target for most people.
     
  5. Tdave

    Tdave Member

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    Cite, please.

    I thought it was supposed to be 80%. I sure hope I'm right and you're wrong.
     
  6. Palpatine

    Palpatine Banned

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    I think it was in the SEC filing for the IPO.
     
  7. Tdave

    Tdave Member

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    Something else I've wondered. When range suffers due to battery age, will we see that predicted in some display number? In other words, will "ideal miles" show something lower and lower when fully charged?
     
  8. ChargeIt!

    ChargeIt! Member

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    Yeah, that's what I too had heard in the early days ...

    (And, James, thanks for posting this! Very useful.)
     
  9. Palpatine

    Palpatine Banned

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    #9 Palpatine, Mar 2, 2010
    Last edited: Mar 2, 2010
    Registration Statement on Form S-1

    Risk Factors. This section typically has the worst case scenario to warn potential investors. So this might be worst case predictions to cover themselves.

    Page 16 (top)

    The range of our electric vehicles on a single charge declines over time which may negatively influence potential customers’ decisions whether to purchase our vehicles.

    The range of our electric vehicles on a single charge declines principally as a function of usage, time, and charging patterns. For example, a customer’s use of their Tesla vehicle as well as the frequency with which they charge the battery of their Tesla vehicle can result in additional deterioration of the battery’s ability to hold a charge. We currently expect that our battery pack will retain approximately 60-65% of its ability to hold its initial charge after approximately 100,000 miles or 7 years, which will result in a decrease to the vehicle’s initial range. Such battery deterioration and the related decrease in range may negatively influence potential customer decisions whether to purchase our vehicles, which may harm our ability to market and sell our vehicles.
     
  10. Tdave

    Tdave Member

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    Well geez, that's disappointing. When I bought I was thinking 80% after 100k miles or 7 years was pretty good, and that I'd be able to let it go longer, probably down to 70% or so before I'd start to care. Now I find out that will happen BEFORE 100k miles and 7 years. Hmph!

    Maybe someone will post some suggestions on how to make the batteries last longer. Oh wait! :)
     
  11. Palpatine

    Palpatine Banned

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    So knowing the best strategy for long term health of the battery pack, it seems easy enough to make a few common sense changes to daily charging habits. This could easily improve your odds of having 80%+ of your original capacity after 100,000 miles.
     
  12. doug

    doug Administrator / Head Moderator

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    Why don't they just change the software so that, in addition to the charge timer and the current limit, the user is allowed to set a target SOC.
     
  13. Tdave

    Tdave Member

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    Is there much benefit, if I charged only to 75% instead of 90%? It would nice to have quantifiable comparisons of the benefits of these things. Something more than just it's better. If I get another 2 months of battery life after 7 years, it's not worth the trouble for me to worry about it. If it's another 2 years of battery life, well that's a different story.
     
  14. Palpatine

    Palpatine Banned

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    I think it will likely result in you having about 10%-15% more battery capacity after 100,000 miles. If the average Tesla owner will have 60%-65% after 100,000 mile by merely charging in standard mode every day (plug and forget), then the obsessive compulsive Tesla owner (that would be me) should be able to improve on that number.

    The basic guidelines on laptop cells is a good guide. A few percentage points of preserved capacity per year can add up significantly over 5-7 years.
     
  15. Palpatine

    Palpatine Banned

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    #15 Palpatine, Mar 2, 2010
    Last edited: Mar 2, 2010
    Excellent idea for a firmware update. They need an advanced user screen with some of these options.

    Ted, I know you are reading this. Why can't we get a screen to set a user defined charge stopping point? Either by SOC or ideal miles?

    Or perhaps give us a lower default point to stop charging. Perhaps 3.9 or 4.0 volts.
     
  16. doug

    doug Administrator / Head Moderator

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    Yeah, some quantitative data would be nice. But certainly, such an option in the firmware would be a heck of a lot less trouble than setting the charge time and rate in the hope of interrupting the cycle at the desired SOC, as has been suggested. Would also give the system a chance to balance the cells.

    As James suggests, it should be an advanced option. If customers want it, they should just do it, unless there is a compelling reason not to.
     
  17. bolosky

    bolosky Member

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    Timed charging

    I decided to try to set my Roadster so that it starts charging late at night rather than as soon as I get home, with the thought that that way it won't be sitting around at a full standard-mode charge all night. The idea wasn't to try to get it to a partial charge, just to have it start later.

    I've never used timed charging mode before, so maybe I did something wrong. I got home, parked the car and set it to start charging at 4AM. I plugged it in and it started charging immediately. I got back into the car and again set it to charge at 4AM. It stopped charging and put up a note saying "scheduled charging at 4AM" or something like that.

    This morning, I got to the car and it hadn't charged. It had a screen that said "plug in cable" or something, even though it was plugged in. I switched it to "charge on plug-in" and it started charging, but it only added 2 ideal miles in the time it took me to take the garbage to the curb.

    Luckily, I have enough charge to get me through the day, so it's no big deal. Still, it's annoying.

    Has anyone else had problems like this? Any suggestions?
     
  18. ChargeIt!

    ChargeIt! Member

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    #18 ChargeIt!, Mar 3, 2010
    Last edited: Mar 3, 2010
    It could happen (possibly buggy firmware) when you change the time of charging or stop and restart charging (sliding the grey switch on the connector off/on) that it won't "take". In that case the safest method is to actually disconnect from the port and most importantly close the cover. Re-open after a few seconds and start over. Better yet, make all the adjustments you want while the cover is closed then re-connect.

    Edit: don't know why it started for 2 miles then stopped (unless you were "full" or in storage mode, or another bug symptom). But closing the cover basically tells the firmware to "let's start over".
     
  19. JRP3

    JRP3 Hyperactive Member

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    I wouldn't be surprised of the 60-65% after 100k/7years is a worst case estimate for the SEC filing, and real world results will be better.
     
  20. malcolm

    malcolm Active Member

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    I understand that the car needs to be plugged in in order to perform cell balancing, but if I'm reading correctly it only seems to do this after a Standard charge.

    Why not after any (non Range/Performance) charge?

    I guess we need more charge settings and names to go with them:

    Range / Performance - Standard - Medium Commute - Short Commute - Economy - Obsessive/Compulsive - Storage

    :biggrin:
     

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