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New 70, comes with a 75 (disabled) would 100% charge ~ 93% charge

Discussion in 'Model S: Battery & Charging' started by blueguse, May 14, 2016.

  1. blueguse

    blueguse Member

    May 14, 2016
    Boynton Beach, Fl
    We all know to help retain the life of the battery we must sacrifice range on daily charge to 90%. If the new Model S 70 is "really" a 75, would charing the battery to 100% really equal 93%? My question isn't if I should change to 100% regardless, just curious about how the artificial lowering of the battery capacity really limits the battery capacity.

    70 kw * 90% = 63 kw
    75 kw * 90% = 67.5 kw
    75kw * 93% ~ 70 kw

    (75 kw * 90%) / 70 kw = 96%
    Therefore a 96% charge of a 70 kw (really a 75) is equivalent to a 90% charge of a 75 kw.

    The hardware should still balance the cells regardless of max capacity and if max capacity is actually higher than the amount you are "allowed" to charge there should be extra room for the cells to balance.

    Any thoughts?

    Again, this isn't a question of IF people should charge their new Model S 70 to 96% just more a question about the physics.
    • Informative x 1
  2. Rockster

    Rockster Active Member

    Oct 22, 2013
    McKinney, TX
    This is much the same conversation that surrounded the 40kWh battery that was really a 60 inside. The consensus seems to be yes, there's a benefit to having the untapped overhead for the reasons you suggest.
  3. gaswalla

    gaswalla P4201/85/airsusp/pano/19i

    Sep 23, 2012
    San Diego
    Yes, this is the reason I see no point in going for the upgrade... You are getting to charge to 100 percent daily for free and without worry.
    Also, the 40s had issues with battery balancing since 40kwh is only 2/3 of the total battery capacity. In this case, 70kwh is over ninety percent of the he total capacity, and balancing issues shouldn't be a problem and battery health should be maintained.

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