TMC is an independent, primarily volunteer organization that relies on ad revenue to cover its operating costs. Please consider whitelisting TMC on your ad blocker or making a Paypal contribution here:

Why only 37 miles of additional range for 20kWh of capacity?

Discussion in 'Model X: Battery & Charging' started by fengshui, Dec 3, 2015.

  1. fengshui

    fengshui Member

    Nov 9, 2012
    Santa Barbara, CA
    Why does the X70D (3.14 Mi/kWh) get so much more range per kW than the X90D (2.85 Mi/kWh)? Is it the reduced weight of the battery pack, different pack utilization, or something else?
  2. MichFin

    MichFin Member

    May 8, 2015
    Detroit, MI
    With the Model S the 70 has lower HP than the 85 so it uses less electricity.
  3. Zextraterrestrial

    Mar 11, 2010
    Humboldt/Los Altos
    #3 Zextraterrestrial, Dec 3, 2015
    Last edited: Dec 3, 2015
    but that is like saying a P85 has more HP and uses more than a S85 which is not true if they are driven the same ....
    S70 3.28 mi/kWhr
    S85 3.12 mi/kWhr
  4. tom66

    tom66 Member

    Dec 17, 2013
    United Kingdom
    Lighter pack & motors, and the battery and motor are optimised for lower power operation so the efficiency of the system is higher.
    It's also possible the 85/90 are cycle-derated to make the 70 seem better, for example the 90 could be capable of more miles but the range computer estimates much less.
    Tesla does this the opposite way around for the 70kWh Model S. It's capable of something close to 250 miles but it's derated slightly to 240 miles to make the 85 and 90 look better.
  5. Saghost

    Saghost Active Member

    Oct 9, 2013
    The difference is real and documented on the Model S, and is greater than the weight alone can account for.

    I asked about this difference (on the S) a while back, and got a lot of numbers supporting the EPA data and a few theories for why, but no one seemed entirely sure.

    I think the X architecture is similar enough to the S that the information provided penalty does accurately reflect the relative range - which makes choosing harder, because not only is it "only 37 miles" for $13k, but you actually have to use ~10% more power/pay more money for all the typical days you aren't on a long trip.
  6. _TTT_

    _TTT_ Member

    May 19, 2015
    The 70kWh battery has 14 modules and the 85kWh battery has 16 modules. Same small batteries in both. The 90kWh changes the chemistry to add 6% range but uses the same 16 modules.

    Using the EPA figures for the X:

    220 miles * 16/14 * 1.06 = 266 miles of range
    The reason the EPA lists 257 miles of range is due to increased weight and also increased power (as EPA testing accounts for faster acceleration). This results in a vehicle which is 3.7% less efficient than the base model 70D because of weight and acceleration.

    Don't get caught up on the exact size of the battery; by using the module count you can see how the numbers really work. 70 and 90 are not exact figures.
  7. Peter Egan

    Peter Egan Member

    Dec 13, 2015
    Artarmon, NSW, Australia
    85kW.h battery has 16 modules in series with each module having 6 cells in series by 74 in parallel (7104 cells). 6% higher amp.hour cells are used to create the 90kW.h. The new cells must deliver 3.3a.h compared to 3.1a.h for the older cells. However, both cell types have a higher nominal amp.hour rating (3.5 a.h and 3.3 a.h respectively). Thus both 85 kW.h and 90 kW.h batteries have 74 cells in parallel. 70 kW.h battery would suffer a 12.5% voltage drop if the 14 modules have a similar architecture to those in the 85.kW.h - 6216 cells (84Sx74P). The modules may only have 70 cells (total 5880 cells) in parallel otherwise the 70 kW.h battery would have 74 kW.h.

    3.6V per cell is the midpoint of the cut-off voltages (3.0V and 4.2V). The voltage difference between charged and near empty charge is 30%. The current needs to go up as the battery runs down to compensate for the voltage decline.

Share This Page