Electric Vehicle Technology: Electricity consumption of electric cars
It is not easy to derive the actual consumption and range of electric cars from the technical data for the traction batteries and the drive alone. As a traction battery, the battery is designated for driving an electric or electric hybrid vehicle, since at the same time there is also a commercially available on-board power supply battery, which is known from the incinerator passenger car.
To compensate for the extreme temperature fluctuations in winter and summer operation in the passenger car area as best as possible, cooling and, ideally, heating of the traction batteries is necessary in order to keep them in an optimum operating range for the efficiency. In the case of corresponding systems, electric cars limit the useful energy for the actual drive. Furthermore, the traction batteries are operated only to a certain extent of their capacity, so they are never completely discharged and generally not charged to a maximum. This is why one speaks of a so-called load window.
According to Nissan and Tesla, according to customer surveys, this battery management of electric car is capable of running between 150,000 and 200,000 kilometers to a residual capacity of around 80%, which is generally considered to be the limit where a traction battery is considered consumed. In addition, a number of car manufacturers are currently developing concepts for the recycling of power cells which are no longer fully capable of being used as stationary storage, for example for households with photovoltaic systems.
Electric charging technology has an additional effect on the effectiveness of an electric vehicle. On the one hand, the charging loss is higher with higher charging currents; on the other hand, rapid charging reduces the service life of the batteries to a certain extent. The temperature also affects the consumption of an electric car. In the winter, charging losses of up to 30 percent can occur – for example, when a tanking process of 15 kWh of battery capacity exceeds 19 kWh, electricity is consumed. And here, too, it will be up to the manufacturers to achieve the most effective loading of their products in order to stand out from the competition.
Operation of the motors in electric cars
Three-phase AC motors are used in practically all electric cars on the drive side. Three-phase alternating current, correctly referred to as “three-phase alternating voltage”, is known in our household as the “heavy current” connection of a kitchen stove. The type mentioned in the technical term “inverter-driven permanent magnet-excited three-phase synchronous machine” has, inter alia, advantages due to less wear because no abrasive contacts are required. The inverter has two tasks: In thrust mode, it converts the energy from the traction battery into alternating current. During recuperation, where the electric motor operates as a generator, it again serves as a rectifier for the charging current to the battery.
Other engine concepts (DC motor, inverter-driven asynchronous motor) are currently playing virtually no role in the electric car. The difference between synchronous and asynchronous motors lies in the operation of the “rotor”, i.e. the rotating part of the motor. In the case of asynchronous motors, the rotor follows the stator rotation field as a function of its function as a generator or motor, i.e. it is asynchronous. In the case of the synchronous motor, the rotor runs immediately synchronously with the stator rotation field.