Why a Single Speed Gearbox is Perfect for All Light-Duty Electric Cars and Trucks
Torque from the motor goes through and is compounded (multiplied) by the ev transmission or gearbox and differential gears, jointly referred to as “final drive ratio” or (FDR). Electric motors have a much broader torque band than do internal combustion engines, in fact, most make full torque right up from zero rpm. Electric motors do have a sweet spot where the efficiency is at its highest but in light-duty vehicles the torque is strong across the normal rpm range, here multiple speeds are unnecessary and would be a complete waste of money.
Midsize and large trucks (class 5 and above) find benefit from multiple speed transmissions but class 4 and below can be quite efficient and have amazing performance with a single speed gearbox.
Internal combustion engines (ICE) rely on rpm increase to get in the peak torque of the engine. Then through multiple speed gearboxes or automatic transmissions with torque converters try to keep the rpm high while accelerating. Without the multiple speeds close together their acceleration and efficiency would suffer greatly.
ICE example - Most ICE vehicles today have between six and ten forward ratios to create decent acceleration and also provide cruising economy by squeezing the maximum efficiency out of every gallon of fuel.
ELECTRIC example - Tesla cars have awesome acceleration and top speeds as high as 163 mph and they accomplish this with one forward ratio (no shifts). In fact, most all-electric light duty vehicles have only one forward ratio, simple is good. Some manufactures refer to not having a transmission at all but they do have a reduction gearbox sometimes called a reducer.
Having a high FDR allows the use of smaller more economical motors. Too much ratio, however, will limit the vehicle’s top speed, what is referred to as being gear bound. We suggest you choose your FDR to allow the desired vehicle top speed, then choose the motor size and pack voltage for the acceleration performance you desire.
Help with these calculations and decisions can be found by contacting us online or by calling our tech staff with your questions at 623-755-8214.