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 or making a Paypal contribution here: paypal.me/SupportTMC

Does the performance degrade with battery age?

Discussion in 'Model S: Driving Dynamics' started by jhs_7645, Aug 6, 2012.

  1. jhs_7645

    jhs_7645 VIN: #3305

    Joined:
    Jul 1, 2012
    Messages:
    451
    Location:
    Camas, WA
    Since it seems that 0-60 times are tied to the output of the battery (40kWh == 6.5, 60kWh==5.9, 85kWh= 5.6), I'm wondering if the performance (0-60 times) degrade as the battery's max range capacity decreases over time?

    The reason I ask is to help me with my decision regarding performance version v. non-performance version. I plan on having this car for a long time, and nothing I've seen says that the inverter can be upgraded later. Also, as larger battery packs come out in the future, assuming they will be offered as replacement batteries, will that also affect performance?
     
  2. AndyM

    AndyM Member

    Joined:
    Apr 10, 2012
    Messages:
    661
    Location:
    Sherwood, OR, USA
    My assumption would be no. The battery isn't the different component in the Performance model, its the inverter. I would expect the range, not the current pulled from the battery, to degrade over time.
     
  3. jhs_7645

    jhs_7645 VIN: #3305

    Joined:
    Jul 1, 2012
    Messages:
    451
    Location:
    Camas, WA
    How would that explain the disparity among the other versions? Do they all have different inverters? Is that an assumption, or something that we know to be true?
     
  4. ggr

    ggr Roadster R80 537, SigS P85 29

    Joined:
    Mar 24, 2011
    Messages:
    2,479
    There is a limit to how much current you can pull from each cell. The smaller batteries have either less, or smaller, cells, therefore you can not draw as much current from the battery as a whole. To a very close approximation, the current you can draw at a particular voltage won't change very much until the cell(s) start to really degrade. The difference between the normal and performance versions of the 85kWh models seems to be a beefier inverter, I think the inverter for all the non-performance models is the same.
     
  5. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

    Joined:
    Mar 8, 2012
    Messages:
    12,755
    Location:
    Texas
    My understanding is that the inverter pulls a given maximum amount of current from each cell (each sheet actually). The more cells there are in a battery the more current the inverter can pull. Because the voltage of the individual cells remains constant throughout the useful life the cell, the maximum amount of power the inverter is able to draw remains more-or-less constant. So the number of cells dictate the amount of power that the inverter can draw (up to the maximum allowed by the inverter).
     
  6. AndyM

    AndyM Member

    Joined:
    Apr 10, 2012
    Messages:
    661
    Location:
    Sherwood, OR, USA
    Which would explain the varying 0-60 times:

    4.4 perf, 5.6 non-perf (85kWH), 5.9 (60kWh), 6.5 (40kWh)
     
  7. jhs_7645

    jhs_7645 VIN: #3305

    Joined:
    Jul 1, 2012
    Messages:
    451
    Location:
    Camas, WA
    Interesting... it would be nice to have that confirmed, are there any roadster owners with degraded batteries that can comment?
     
  8. jhs_7645

    jhs_7645 VIN: #3305

    Joined:
    Jul 1, 2012
    Messages:
    451
    Location:
    Camas, WA
    One more note (not to drag this out) is from Tesla's FAQ:
    Note that it says 70 percent of initial performance levels...
     
  9. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

    Joined:
    Mar 8, 2012
    Messages:
    12,755
    Location:
    Texas
    The European Roadster owner who recently passed 200,000 km indicated that about 70% of his range remained--my understanding is that he races his Roadster regularly so his is a worst-case scenario. Because he was racing when he passed the 200,000 km mark I really doubt his performance was down 30%.
     
  10. VolkerP

    VolkerP EU Model S P-37

    Joined:
    Jul 6, 2011
    Messages:
    2,455
    Location:
    Germany
    Cell degradation increases internal resistance. This will increase voltage sag. Example: when drawing 1200A, pack voltage will drop from 400V to no just 330V but to 270V. This will reduce power output.
     
  11. Doug_G

    Doug_G Lead Moderator

    Joined:
    Apr 2, 2010
    Messages:
    15,852
    Location:
    Ottawa, Canada
    When a Roadster gets down to 50% charge you don't see a significant drop in performance. The electronics can draw a bit more current to make up for the drop in voltage - within limits of course. Obviously if you're trying to do drag racing the pack should be pretty full, but I'd doubt you could tell the difference without instrumentation.

    I doubt you'll see significant performance loss until the battery gets below 70% capacity.
     

Share This Page