AC and DC charging: where electricity is converted

Useful to know

When talking about electric vehicles, "charging" can mean different parts of the system. The station outside, the cable and the on-board unit in the car do not perform the same function. When AC charging the car receives alternating current, which the on-board charger converts to constant for the traction battery. This is described in the AFDC scheme for the electric car. [1] The first useful distinction is therefore where the conversion takes place, not just what the parking lot column looks like.

The onboard charger doesn't work in isolation. It communicates with the equipment and monitors battery characteristics such as voltage, current, temperature, and degree of charge. [1] This explains why energy is not supplied randomly just because the cable is plugged in. Charging is a controlled process with limits from the vehicle. When comparing two cars, one should look at their own capabilities, instead of assuming that the same external point will necessarily give the same result for each model.

In DC charging, the conversion is outside the vehicle and the energy is fed as direct current. The AFDC distinguishes AC equipment and fast DC charging, stating that the time depends on several factors: the available charge, the battery, the equipment power, and the capabilities of the vehicle. [2] Therefore, the maximum power in a station description is only one part of the picture. It should not automatically become the promise of unchanged power from the beginning to the end of each turn.

The published examples of AFDC are about American infrastructure and do not universally describe all contacts and voltages around the world. [2] For a specific route, the appropriate connector, compatibility and charging mode should be checked. This is especially important when one uses information from another country. The general principle for AC and DC is portable, but the practical possibility of including a car at a given point requires a more accurate description of both sides.

Imagine two stops: a long stay at night and a short break along the way. The first may allow slower replenishment of energy, while the second places another time requirement. This is not a recommendation for a particular station, but a way to connect the technology to the use. The energy required, the available stay and the actual capabilities of the vehicle are important. The "quick" label itself does not say whether the particular stop fits the specific travel plan.

When keeping your own observations, it is useful to record the initial and final charge, the added energy, and the duration. Similar cases are then compared, instead of a single unusual session being assumed to be permanent behavior. Thus, the distinction between AC and DC became from a technical abbreviation to a practical understanding of the process. It helps to read the documentation, plan the stay and ask precise questions about the compatibility and limitations of the system.