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Questions about Software limited batteries

Discussion in 'Model S: Battery & Charging' started by RLC3, Sep 4, 2017.

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  1. RLC3

    RLC3 Member

    Joined:
    May 11, 2017
    Messages:
    15
    Location:
    Portland
    I have a 2017 MS 60D, and have some questions about how software limiting the battery is done, and what it really means..

    1) Since the battery is actually a 75, how is the capacity reduced? I have heard two different stories about this. One, that a module is 'turned off', and that they do some sort of rotation (this makes less sense to me). The other that the battery is prevented from being fully charged. Do we know how it is done?

    2) If the state of charge is what is limited, does this mean that it is fine to charge all the way to 100% regularly because it is really only 80%?

    3) What about balancing? I gather this is pretty automatic, but I've seen descriptions of the balancing process that imply the battery needs to get to 93% charge to trigger balancing. Depending upon #1 above, this might never happen with the MS 60s. I would assume that Tesla thought of this and that it is being handled somehow, but does anyone know about this?

    4) If the battery is charge state limited, does this mean that the capacity should stay at a full 60 rather than degrading, even though the battery may have lost some of its 75KWH of capacity?
     
  2. ucmndd

    ucmndd Member

    Joined:
    Mar 10, 2016
    Messages:
    391
    Location:
    California
    1) there was a flurry of upgrades several months ago when the price was reduced to $2k. Someone charged their car to 100%, paid for the upgrade, and when it was done the car reported a SoC of 86%. So that’s pretty definitive IMO.

    2) I won’t offer any opinion on if it’s “fine” to do so other than to say with the above information I’ve decided it is. I charge my 60 to 100% every time. As a data point, my car has 26,000 miles and has lost ~5% of its reported capacity (210mi when new to 200 now).

    3) unknown.

    4) my battery has degraded approx 5% in 25k miles. The software locked “60” does indeed degrade over time and appears to be some fixed percentage of overall battery capacity.
     

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