Reply To: Range question

Aptera Community Aptera Discussions Range question Reply To: Range question

Aptera Community Aptera Discussions Range question Reply To: Range question

  • Joshua Rosen

    Member
    August 19, 2021 at 2:39 pm

    Slower the better, The kinetic energy equation is K = 1/2MV^2 where M is the mass and V it the velocity. The drag equation is related, it’s D = (Cd * r * V^2 * A)/2, where Cd is the coefficient of drag, r is the density of air and A is the area. As you can see from both equations they are a function of the square of the velocity. ICEVs mask this because they are so horrendously inefficient in city traffic, they either keep running when they are stopped or all of the components have to be accelerated back to a working speed when the resume running. ICEs also have very narrow power bands which they mask with multispeed transmissions, this exacerbates their inefficiency at low speeds. Electric motors don’t work that way, they don’t consume any power when they are stopped and they are very efficient at all practical speeds. The other advantage that EVs have is that they can recover a lot of energy when they decelerate via regen braking. Accelerating an object is converting potential energy into kinetic energy. Decelerating is the reverse process, with regen braking you are converting the kinetic energy of the moving car back into potential energy that’s stored in the battery. With friction brakes all of that rolling energy in the car has to be converted into heat which is then lost to you forever. The bottom line is that because EVs have many fewer parasitic losses the basic energy equation dominates so the effects of speed are much more pronounced.