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Range Mode and battery longevity

Discussion in 'Roadster' started by graham, May 23, 2009.

  1. graham

    graham Active Member

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    So I tried to pin Tesla down about this, and they were a little vague.

    I love my car, and I love taking it on little day trips over the weekend. But without the mobile charger, I am very limited in what I can get to and then back to Aptos for charging at night. 2 weekends ago, I needed to go to Livermore, last weekend I went to Big Sur, and tonight I have tickets for a show in San Francisco.

    In all cases, it is just at the edge of where I feel comfortable of having enough range in Standard Mode, so I charge it in Range Mode. They do warn that frequently charging in Range Mode will decrease the life of the batteries, but I don't have a good idea of what that means.

    Is it okay to do once a year?

    Is it okay to do once a month?

    Is it okay to do once a week?

    What constitutes too much Range Mode? Does anyone have any better guidance?
     
  2. WarpedOne

    WarpedOne Supreme Premier

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    Depends on what you mean by OKAY.

    I don't have numbers for exact Li-Ion cells at hand, but I have numbers for Firefly LA battery and they should would work for illustrating the point.

    Oasis states that with 80% DOD (equivalent to Normal mode) you'll get 600 cycles before capacity drops to 80% nominal. With 100% DOD (equivalent to Range mode) you'll only get 400 cycles before capacity drops to 80% nominal. That means 400 charging up to 100% and than discharging to 0% will reduce the capacity to 80%. It will take 600 charging to 100% and than discharging to 20% for same decrease in capacity.

    What if only every other cycle is 100% DOD and others are 80%? You'll get 500 cycles before same capacity drop. If only every fourth cycle is 100% DOD you'll get 550 cycles. If every tenth cycle than you'll get about 570 cycles. You get the point.

    Tesla says their pack should last for 100.000 miles. With normal range of about 200 miles that means about 500 80% DOD cycles with some reserve. I'd say if you only occasionally (less than say 10% of cycles) use Range mode and actually drive out the whole range you are fine - you'll see those 100.000 miles.

    Don't forget its not only charging up to 100% that is hard on the battery. Completely discharging it down is even harder on them. If you're in doubt about range, it's better to put it into range mode and then not discharge it completely than to leave it normal mode and dry it out.
     
  3. doug

    doug Administrator / Head Moderator

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    I think part of the equation is also how long the battery sits at 100%. So if you fully charge the battery and immediately start your trip, I believe that has less of a deleterious effect than if it sat at 100% over night.
     
  4. donauker

    donauker Member

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    According to this Blog entry, Tesla does not charge to 100%, Range mode is limited to 95% max SOC and to 3% minimum SOC. Standard Mode is 90% max SOC and it would appear to be about 10% minimum.

     
  5. graham

    graham Active Member

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    #5 graham, May 24, 2009
    Last edited: May 24, 2009
    In case anyone was wondering, I did make it to San Francisco, watched Spamalot and made it home with no problem. It was 177 miles round trip in Range Mode.

    I took highway 1 the whole way so I could go slower. For most of the trip I had the cruise control set at 50mph, and when I had to stop and start, I accelerated very slowly. When I got home, I had 42 miles left on the estimated range (and 47 on the ideal range).

    Hopefully the batteries did not suffer too much.

    (Buy a hot sports car so you can drive like your grandmother! whee!)
     
  6. Palpatine

    Palpatine Banned

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    So for the trip there you started in range mode with torque 50% limited? But likely for the trip back, since you turned the car on with around 60% SOC, you were in normal standard operating mode?

    Do I correctly understand how the Tesla operated in this scenario?
     
  7. graham

    graham Active Member

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    No, I am pretty sure the VDS reminded me that I was torque limited when I got back in for the drive home. I think it must only reset to Standard when you next actually charge - although I would want to experiment again before I state it for sure.

    The ride home did have to deal with headlights and the heated seats which the drive out did not.
     
  8. ChargeIt!

    ChargeIt! Member

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    :biggrin: !! (ROFL)
     
  9. dsm363

    dsm363 Roadster + Sig Model S

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    Does the battery only discharge down to a certain percentage (~20%) if you don't have the max range mode on? Trying to get an idea of a safe range for a Tesla (I'm ordering Model S but same concept) so with 300 mile battery pack is it (300miles x 80%) x 1/2 to get farthest distance I could go with that pack? Thanks.
     
  10. Kevin Harney

    Kevin Harney Active Member

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    Yes the pack only discharge to a certain degree. Not yet determined for the Model S. But in general the range for the Roadster seems to be about 70-75% of the stated Ideal range. And it is said that packs tend to lose 10% over a 5 year period. So, therefore, a 300 mile pack could be expected to go about 210 miles max new on the highway and more like 190 miles after a few years. These calculations are based on a conservative approach but I think they are pretty realistic. That is the problem with giving ranges based on EPA. But not really anything we can do about that.
     
  11. BillB

    BillB Member

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    FWIW, I took a long weekend trip in Range mode (both ways, with an overnight boost in the middle), and I arrived home with 19 miles left in the "tank." When I switched to Standard mode in my garage before recharging, it told me that I had already run out of juice and stopped some time back.
     
  12. Kevin Harney

    Kevin Harney Active Member

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    So Bill,

    Could you have traveled in "normal " mode and done the opposite?!?! Run out of charge and switched to Range mode and had a few miles left to get you the last bit home ? Kind of an emergency battery supply if REALLY necessary ?
     
  13. doug

    doug Administrator / Head Moderator

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    I've tested that and the answer is yes.
     

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