Submitted by martinwinlow on Thu, 2010-08-26 03:22
Anyone care to offer an opinion on what speed the range for the various battery options is based on? I couldn't find anything on the T website about this.
In case you are wondering why I ask, range decreases at an exponential rate with reference to speed. An easy to remember example of this is: if you drive at 50mph you use almost exactly half the power (and therefore fuel) that you do driving at 70mph. I am talking about true 50mph and 70mph here, not what your speedo says as there are notoriously unreliable at higher speeds - and on a level road with no wind.
If you want to test this theory, use a GPS based speedo at least and one with a good signal. Or have a look here... http://www.evconvert.com/tools/evcalc/ ...and you can play with the numbers to your hearts content.
Incidentally, this exponential decrease in range is almost entirely dependent on the frontal area of the vehicle - the area you would get if you took a front (or rear) elevation drawing of the vehicle and measured the total area of the vehicle including wheels and wing mirrors but excluding the space below the vehicle, between the wheels. The formula is... Drag force = 0.5 X density of air X speed squared (the exponential bit) X coefficient of drag (Cd) X frontal area.
One way the Model S minimises the Cd is to have a very smooth belly pan. 99% of vehicles have a very rough one and this induces a good 10% increase in drag ie reduces the miles per gallon performance by 10%.