How an electric car works: battery, drivetrain and charging

Useful to know

The all-electric car stores energy in a traction battery and uses it for electric wheel drive. This distinguishes it from a hybrid where the electric part works in conjunction with an internal combustion engine. When looking at its design, it is useful to monitor the path of energy: from the external power supply to the battery and from it through the control electronics to the motor. Thus, individual components are given a clear role, instead of looking like a list of technical abbreviations. [1]

The traction battery powers the electric motor, and the power electronics control the flow of energy and respectively the speed and torque. The drivetrain connects the motor to the wheels. There is also an auxiliary electrical system in the car: the DC/DC converter supplies a lower voltage for electrical loads and for the auxiliary battery. A separate temperature system maintains appropriate operating conditions for important components. Therefore, having a large battery does not eliminate the need for control, cooling and auxiliary power. [1]

When charged with alternating current, the on-board charger converts it to direct current for the traction battery. It also participates in communication with the charger equipment by monitoring process parameters. During regenerative braking, the electric motor can also act as a generator. This allows some of the energy recovered during deceleration to be reused. However, the presence of such a function should not be understood as a way for the car itself to provide all the energy for the next trip. [1]

For practical use, it matters where the car spends its time. Charging in a place where it stands for a long time, and a short stop along the way are different tasks. The U.S. AFDC Center considers public stations on both long-stay sites, such as hotels and workplaces, and along transportation corridors. This distinction is also useful outside the U.S.: charging infrastructure must match usage patterns. However, U.S. names at charge levels should not automatically be carried over as European technical standards. [3]

Battery capacity and power are different quantities. The kilowatt-hour describes an amount of energy, and the kilowatt describes power. As a purely arithmetic example, if usable capacity is 60 kWh and the consumption is exactly 20 kWh for 100 kilometers, the ratio gives 300 kilometers. This is not a promise of the actual range on a specific model. The example only shows why a capacity figure without consumption data is not sufficient for comparison. When buying, specific cars must be compared under comparable conditions.

The costs are also not reduced to one characteristic. AFDC looks at purchase price, energy efficiency and charging conditions together. For personal evaluation, it is more useful to use their own routes and actual energy prices, rather than a general statement that any electric vehicle is necessarily the cheapest. Knowing the design helps with precisely these questions: where the energy comes from, how it is used, where it can be restored, and how the daily mode combines with the accessible charging. [2, 3]