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Battery Capacity Available

Discussion in 'Model S: Battery & Charging' started by tomanik, Jan 27, 2013.

  1. tomanik

    tomanik Member

    Joined:
    May 30, 2009
    Messages:
    272
    Location:
    Canada
    I have ordered a 60 kwh battery and have been trying to understand when the range indication reaches 0, what is really left in the battery. From what people have reported previously with the 85kwh battery it appears that 5kwh is being reserved or most maybe just limiting usage. As the battery gets smaller does the available capacity remain a constant as a percentage

    85kwh
    -------
    Total Capacity: 85kwh
    EPA Range: 265 miles (range mode charge)
    Reported Energy Usage: ~80kwh of energy running the range to 0 or close to it (as reported by the car)
    300 wh/mile
    Reserved/Restricted: 5kwh (5.9%)
    So the extra 5kwh is hidden, some at the top, some at the bottom?

    60kwh
    -------
    Total Capacity: 60kwh
    EPA Range: 208 miles (range mode charge)
    Reported Energy Usage: TBR
    ? wh/mile
    Reserved/Restricted: 5kwh (?%)


    60kwh
    -------
    Total Capacity: 40kwh
    EPA Range: TBD miles (range mode charge)
    Reported Energy Usage: TBR
    ? wh/mile
    Reserved/Restricted: 5kwh (?%)

    I appreciate no one here will know for sure but interested in opinions.
     
  2. Jason S

    Jason S Model S Sig Perf (P85)

    Joined:
    Apr 20, 2012
    Messages:
    1,350
    Location:
    Rocklin, CA
    I think some of the bottom end is hidden, mostly to prevent bricking even if one does drive it till it doesn't go anymore. No reason to hide some of the top, except for 'range' mode. I expect that bottom amount to be fixed, not variable or a percentage. It is simply the battery maintenance buffer.

    The 60 may have gotten new firmware versus testing with the 85, accounting for the slightly higher efficiency. That new firmware should be available to all versions.
     
  3. ChadS

    ChadS Petroleum is for sissies

    Joined:
    Jul 16, 2009
    Messages:
    2,401
    Tesla has gone out of their way to NOT say how much of the battery is held in reserve. For my calculations I usually assume 81.5kWh are available of the 85kWh pack; that seems to fit all the numbers I've seen.

    Incidentally, if you set Tesla's range calculator to 60mph, 70 degrees with HVAC on, you'll get 269 miles for 85kWh, 208 miles for 60kWh, and 143 miles for 40kWh. So that should give us some idea of the EPA rating for the 40kWh pack.
     

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