E-Mobility Glossary

BEV is short for ‚battery electric vehicle‘. When we talk about these vehicles, we often only say ‚EV‘ (electric vehicle). Strictly speaking, this is incorrect. Because EV is the umbrella term for all vehicles with an electric power system, from e-scooters to fuel cell electric vehicles (FCEVs). The difference is in the way they store energy. While most EVs now use a battery as their storage medium (BEVs), vehicles with fuel cells use hydrogen or methanol. What all EVs have in common is that they are powered by a purely electric system with one or more electric motors—some are fed with electricity from batteries, while others use tanks and a fuel cell that generates electric energy on board.

Bidirectional charging generally means the use of the vehicle battery for external consumers. The energy stored there feeds not only the electric motor and the usual car equipment but also e.g. a vacuum cleaner or refrigerator. It is also technically possible to supply the entire building with electricity. Theoretically, bidirectional charging can go as far as using the electric vehicle’s battery as a system buffer. In that case, electricity from the grid is stored in the vehicle battery during peak production and fed back into the grid during peak consumption. This reduces the grid’s load and makes for a better use of electricity from renewable sources.

Calibration is the legally prescribed testing of a measuring instrument for compliance with calibration-act guidelines, in particular the calibration error limits. In order to legally pass on electricity charging costs to customers, tenants, or employers (in case the company vehicle is charged at home), a calibrated meter must record the electricity that has been charged. In theory, this is possible with a separate energy meter connected upstream of the charging station. This solution, however, is complex and expensive and cannot record the consumption for individual charging sessions in isolation. Wallboxes with an integrated calibrated meter are the simpler solution. In Europe, an MID-certified meter is usually sufficient, but in Germany, the meter must comply to the stricter requirements of the national gauging and calibration act. Devices with this type of calibration are marked with the acronym ME for Mess- und Eichrecht, often visible from the outside.

Charging power is an important factor for the charging speed. Mainly limiting the charging power, along with various external factors like outside temperature, charge level, and the charging station’s power, are the battery’s constant internal factors (size, cell chemistry, and architecture) as well as the charging management. Ideally, the limiting component is always the vehicle. So, the charging power of e.g. an e-scooter is only a few kilowatts, while other e-vehicles are able to handle the power of more than 300 kW. Since a battery can never be continuously charged with high power, these figures are maximum values—a peak performance that can only be held over a few short minutes. What’s more significant is the average charging power, especially at a state of charge (SoC) between 10 and 80 percent. In practice, however, the loading system is often a power limiter. The power (P) is the product of electric current (I) and voltage (U). A domestic wallbox with a 3-phase plug therefore has a maximum output of 16 A × 3 × 230 V = 11 kW. This is sufficient for charging overnight and preserves battery life. DC fast chargers, on the other hand, can generate power of up to 400 kW in theory (500 A × 800 V) and are therefore the best choice when it comes to travelling long distances.

DC is short for ‚direct current‘. Directly above you can find out what DC means.

If a battery is deeply discharged, it means the power is almost completely drained from it. As deep discharge may have irreversible effects on the battery, it should be avoided whenever possible. The battery management of modern electric vehicles prevents battery use until deep discharge. After prior warning and steady power reduction, an electric car or electric motorbike therefore shuts itself down completely.

Direct current (DC) is when the electrons flow in one direction only. Batteries deliver direct current, and so do photovoltaic systems. If consumers are plugged in, the electrons travel from the anode (minus) to the cathode (plus). The public power grid, however, operates with alternating current (AC), as it allows for a low-loss voltage change. This is why a rectifier is needed when charging electric vehicles with alternating current, for instance via a wallbox at home. The rectifier turns alternating current into direct current, AC into DC. Every e-car has one. If energy is drawn from the battery, an inverter converts DC back into AC, as the electric motor requires it.

An energy meter measures the electricity that flows through it. So, it detects power that is generated, for instance by a PV system, as well as the consumption, for instance at home. In contrast to a regular electricity meter, an energy meter is an electronic sensor. The term often describes the smart version of an electricity meter, capable of communicating with other components, such as the wallbox. An energy meter in this modern sense is definitely needed if one wishes to optimise the energy management of a building.

Excess PV charging is short for excess photovoltaic charging. In this process, self-produced solar energy that isn’t used in the building is fed into the electric vehicle. The excess power is not (entirely) fed into the grid, as is otherwise customary. This direct consumption can significantly reduce energy costs, as feed-in tariffs are often lower than the overall costs of electricity obtained from the grid. This can noticeably shorten the payback period of a PV system.

There are different types of excess PV charging. Basically, we can say that the more intelligent the management – this is where the communication between the PV system, the building, and the charging station comes into play – the higher the share of self-generated power. Which in turn increases your independence from the power grid and reduces consumption costs.

In the context of e-mobility, fast charging means charging a vehicle battery with higher charging capacity, usually using direct current (DC). However, there is no concise, universally valid definition. Because fast charging almost always uses DC, we can assume a value above the country-specific and model-specific maximum AC limit value. (For instance, there are vehicles that can charge with a maximum of 22 kW AC but only a maximum of 43 kW DC. Other models charge AC with a maximum of 11 kW, yet DC with 200 kW. The same vehicles only allow low AC capacity in some countries.) Fast charging can thus be understood as “charging with DC and a capacity beyond the AC maximum.” Fast-charging stations are often found along arterial roads like motorways. Currently, their charging capacity goes up to 350 kW.

‘FI circuit breaker’ or ‘FI-protection switch’ are still common terms for a protective device that interrupts the circuit in the event of a fault current. F stands for 'fault', I for the physical unit of the current intensity.  In the meantime, one speaks of a residual current device, abbreviated as RCD (for 'Residual Current Device').  The RCD detects if something is being lost in a current circuit. In a closed circuit this may not be the case. Thus it protects humans (and animals) from being exposed to large currents permanently. If, for example, current is dissipated through the body by contact with a conductor, a so-called differential current is generated. If this is too large - the maximum value is specified on the RCD as In - the circuit breaker interrupts. All KEBA wallboxes are equipped with DC leakage detection. This significantly reduces the costs of the installation, since only one type A RCD needs to be installed instead of an expensive type B RCD.

High-power charging is a special type of fast charging. It describes power charging in the triple-digit kilowatt range. Currently, HPC covers the power range between 100 und 350 kW.

W stands for ‚watt‘, the unit with which to measure the physical quantity of power (P). While a dustbuster might need 700 W, much higher power is required to drive a car. To keep the figures manageable, we use the unit kilowatt (kW), which is equal to 1,000 watts (≙ 1.36 hp). Two power categories are important for battery electric vehicles: the driving power (the engine power) and the charging power, which is an essential factor when talking about charging speed. The maximum theoretical charging power is limited by the charging station’s output (in a domestic socket that’s only 10A × 230V = 2.3 kW) as well as the battery or the vehicle’s own charge management. The limits diverge wildly and range from a few kilowatts to more than 300 kW.

Wh stands for ‚watt-hour‘, the unit with which to measure how much energy a system consumes or gives off per hour with the power of one watt. In the context of battery electric vehicles, it is used mainly to indicate the battery capacity. To keep the figures small, we use kWh (=1,000 Wh) instead of Wh. A battery with a capacity of 50 kWh is capable of giving off the power of one kilowatt for fifty hours. This is a theoretical value, as the engines especially of electric cars release far greater power—when accelerating over short periods of time this could be several hundred kW, depending on the vehicle type. Yet the theoretical value illustrates well how a battery with twice the capacity can also give off energy for twice as long and can thus also store twice as much energy.

The Measuring Instruments Directive (MID) is an EU guideline specifying the requirements of measuring instruments. With the introduction of the MID, calibration in state-approved testing centers has been replaced by the manufacturer’s declaration of conformity. The calibration’s validity period continues to be based on national regulations. Only MID-certified energy meters may be used for billing electricity costs - with the exception of Germany, where stricter requirements must be met, and the energy meter must comply to the standards put forth in the country’s gauging and calibration act (ME).

Find more information under excess PV charging

RCCB is short for ‚residual-current circuit breaker‘, which is still often called by its older term RCD (residual-current device). It is a safety device that breaks an electrical circuit in which leakage current has been detected. The RCCB identifies a loss in the electrical circuit. In a closed circuit, loss is impossible. And so, the RCCB protects people (and animals) from long exposure to high currents. If a person touches a conductor and electricity discharges into the body, it leads to so-called “residual current.” If it is too high—the maximum value is noted on the switch as In—the switch breaks the circuit. All KEBA wallboxes are equipped with DC leakage detection. This reduces the installation costs considerably, as it requires only a Type-A switch instead of the expensive Type-B RCCB.

The state of charge describes the amount of energy available in a battery in relation to its overall capacity. That’s why it is expressed in percent. An SoC of 80 percent in a 50-kWh battery corresponds to 40 kWh of useable stored energy. In a battery with a 100-kWh capacity, it would be 80 kWh.

Vehicle-to-Load is a special form of bidirectional charging. It means using the energy stored in the electric vehicle to supply external consumers like vacuum cleaners, saws, etc. Because of its diversity of use, we also call it Vehicle-to-Utility. The electric car serves as a large power bank of sorts for electrical devices. The energy is taken either from the power outlet or via an adapter plugged into the connector.

Vehicle-to-Vehicle refers to a special form of bidirectional charging. It refers to the extraction of energy from one electric vehicle’s battery to charge another. The electric car functions as a charging station to supply other vehicles that are low on battery with electricity.

Vehicle-to-Home is a special form of bidirectional charging. It refers to the use of the energy stored in an electric vehicle’s battery for consumers within an apartment or single-family home. The electric car thus supplies a household with electricity. In this way, self-produced electricity, e.g. from your own PV system, can store electricity in times of low demand and high production rates for later use. This makes you less dependent on grid electricity, can lower consumption costs, and helps to reduce grid load. If the batteries of more than one car are used to supply larger buildings with energy, we call this Vehicle-to-Building. It works the same, but consumption and storage capacity are scaled.

Vehicle-to-Grid is a special form of bidirectional charging. It refers to the use of energy in an electric vehicle’s battery as buffer storage for the entire grid. In this way, electricity can be stored during periods of low demand and high production rates for later use. On one hand, this increases the use rate of electric energy from regenerative sources such as PV and wind energy, which only occurs temporarily. On the other, it helps this technology to reduce grid load. The use of existing storage capacities in electric cars also reduces the need for large, invasive and expensive storage systems such as pumped storage.

Web interface (or web user interface, WebUI for short) is an online site that lets you monitor, control or configure specific systems or devices in a web browser. The KEBA web interface allows you to access individual KEBA wallboxes or a group of wallboxes, provided that the device is connected to a network.