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Algorithm Error -- A Different Twist?

Discussion in 'Model S: Battery & Charging' started by ForeverFree, Feb 21, 2016.

  1. ForeverFree

    ForeverFree Member

    Jul 9, 2015
    Sherman Oaks, CA
    Hi, All.

    I've read the various posts on this topic with interest, and share the general sense:

    Seemingly-excessive degradation is 25% actual degradation, 75% range algorithm error.

    Range charging can reduce the latter ... but with some small peril to the former. Not worth it for illusory gains.

    However, even if it's psychological, it's still distressing to see range decline week by week.

    Recently, I had an experience which appeared to clarify what's really going on.

    My 85D's 80% had begun life at 216.

    It was now 206 ... perhaps 208 with range mode on.

    The 206 seems to be right ... but the 80% wrong.

    Please allow me to explain. I did a range charge, with range mode on.

    Charged to 264 (vs. 271 or 272 new).

    Kept charging for quite a while after displayed range stopped increasing.

    Stayed at 264 for about six miles after I started driving.

    All of this has been reported before by many others. Here's where it gets interesting, though.

    Took a no-traffic, constant-speed 38-mile freeway drive to golf course. Reliably uses 42-43 range miles in warm weather.

    Drive was same length as usual, at same speed.

    However, arrived at course with 229 range miles.

    Absent a magical tailwind (which didn't exist), there's no way that the car suddenly managed the drive with using only 35 range miles.

    Hence, the real starting point must have been 229 plus 42 or 43 = 271 or 272.

    When our cars show 234 at 90%, rather than the original 243-245, we assume that the range algo is underestimating the 234.

    Perhaps, though, the 234 is correct. Perhaps the algo is over-estimating the 90%, over-estimating the SOC.

    Why does this distinction matter? Because, if the algo is over-estimating SOC, we really are beginning our drives with fewer miles. 208 is not really 216. 80% is really 77%.

    Just a theory. What does everyone think?
  2. msnow

    msnow Active Member

    Jul 14, 2015
    Doesn't work that way for me. No over-estimation or underestimation. Just patiently waiting for the fix.

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