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Increasing Wh/mile assumption used for rated miles as range goes down

Discussion in 'Model S: Battery & Charging' started by dirkhh, Sep 2, 2013.

  1. dirkhh

    dirkhh Middle-aged Member

    Jul 7, 2013
    Portland, OR, USA
    Playing with the data I am storing from the Tesla servers and figuring out interesting things to visualize I stumbled across something interesting. I think I saw a post about this topic either here or on the Telsamotors forums somewhere, but couldn't find it searching...

    When displaying the rated range the Tesla is not applying a straight linear equation to the remaining battery capacity. Instead it appears to 'hide' some capacity from the user as it approaches zero.
    For example, in my S60 at 90% it gives me 185 miles of range or an assumed 292Wh/mile. But when I'm down to 50% it' tells me I have 94 miles of range (319Wh/mile). And at 11% it claims that I have only 9.5 miles left (695Wh/mile).
    If we assume that the 292Wh/mile as fixed that means that for the 9.5 miles in the end we'd need only 4.6% SOC - so more than 6% of SOC are hidden from the user - that's 3.6kWh or enough to drive more than 12 miles!!!
    Or put the other way around, at 11% capacity it should show more than 22 miles of range.

    Now all these numbers change if you assume that Tesla wants to keep at least n% of charge in the battery to prevent it from bricking. But then the displayed range at 90% is dishonest. And regardless what "brick prevention" ratio you assume, it's still clearly not included in the initial rated range shown.

    I know that some people have truly driven their cars until they stopped. Did any of you happen to collect telemetry data from the Tesla API that day? I'd love to peek at those data.
  2. gregincal

    gregincal Active Member

    Oct 26, 2012
    Santa Cruz, CA
    Other people have observed the same thing. See the Energy Accounting thread. They seem to count down more quickly to provide some "drive after 0" range without having decreased the total range they show.

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