Electric Car: Efficient under the Hood
Author: Joachim Geiger
If it were just a matter of aesthetics, an e-motor could hardly compete against the elegance of a six-cylinder. Since it’s basically comprised of compact housing, magnets, copper wire, and a shaft – the potential for a grand spectacle is rather limited. E-motors have to impress with their inner values. And they have plenty of those.
- Good to know: E-motors can also operate in generator mode. In this case, they convert mechanical energy into electrical energy during deceleration, thus charging the battery. This so-called recuperation increases the range of the electric car. This is particularly efficient where braking is required more frequently – for example on routes with downhill gradients or in city traffic with frequently changing speeds. Experienced drivers can achieve up to 20 percent more range by cleverly using recuperation, estimates DEKRA expert Andreas Richter.
- Good to know: Efficient motor performance in all driving situations. Theoretically, an electric motor can also demonstrate its full performance capability when reversing or recuperating. However, as DEKRA expert Richter explains, manufacturers design the characteristic curves of their electric motors in such a way that safe driving behavior is always possible and the technology can be used with little wear. For this reason, electric motor power is usually greatly reduced immediately when when reversing and recuperating. Energy-efficient use of the electric motor is also easy to achieve on the highway. All that is needed is to reduce speed – this reduces air resistance, which increases quadratically with speed.
- Good to know: The transmission is becoming increasingly important in the e-car. Volkswagen equips the ID3 with a single-stage transmission. Since the electric car reaches a top speed of 160 kilometers per hour at a maximum of 16,000 revolutions per minute, a solution was needed to achieve a transmission ratio to slow-speed for the revolutions of the drive shaft at the wheel. To save installation space, engineers use two smaller gears instead of one large gearwheel, which function as an intermediate gear ratio. Automotive suppliers are also coming up with their own developments. Bosch, for example, has just joined forces with Eindhoven University of Technology to develop an automatic transmission that continuously adjusts the speed and torque of the e-motor to the speed of the vehicle.