Electromobility and the car battery from A to Z

The abbreviation “AC” stands for "Alternating Current". AC is a type of electrical energy that regularly changes direction. In comparison, DC stands for "Direct Current". Here, the current always flows in the same direction. When charging a car battery, both AC and DC can be used, depending on the type of charger.

The battery is the energy storage device and thus the heart and also the most expensive single component of an electric vehicle. The battery capacity is a decisive factor for the range. Batteries age - even when they are not used. Their maximum storage capacity reduces over time (calendar ageing) as well as depending on the number of charging cycles (cyclical ageing). To avoid confusion with the starter battery, we also speak of the traction battery, drive battery or high-voltage battery.

The battery management system (BMS) is responsible for controlling and monitoring the traction battery and the charging and discharging processes. It can reduce the power if necessary, for example when the state of charge is low or a very traction battery temperature.

The abbreviation "BEV" stands for "Battery Electric Vehicle" and has been used by manufacturers for electric cars for some time. To be distinguished from this are "PHEV" (link to corresponding entry).

The first electric vehicles already have bi-directional charging technology, which means that they can not only take in electricity but also feed it back into the grid. With this capability, manufacturers plan to use electric vehicles as part of smart grids. One example would be to temporarily store surplus electricity from renewable energy sources such as solar panels in the battery of the electric vehicle to deliver it either to the grid or back to the home when needed.

In order to charge the electric vehicle with electricity from the grid, an on-board charger is required, which converts the alternating current into direct current for the battery. Depending on the power of the charger, the charging process can be faster or slower. An 11-kW on-board charger, for example, can charge on three phases with 16 amps each, while a 3.7-kW on-board charger uses only one current phase with 16 amps. Single-phase charging using the weaker charger will accordingly take longer compared to three-phase charging.

The Chademo fast-charging system is based on the Japanese standard and predominantly enables charging powers of up to 50 kW. In Germany, only Nissan and Mitsubishi still offer this system, while newly introduced electric vehicles in Europe rely on the CCS standard. For this reason, more and more fast charging stations no longer offer a Chademo charging cable.

The Combined Charging System is a charging technology for electric cars that is widely used in Europe and is now considered the standard. It combines plugs for fast and slow charging in one socket. For charging with alternating current, only the upper part of the socket with the Type 2 plug is needed. For fast charging at corresponding DC charging stations, a significantly larger plug is additionally inserted into the two DC poles below the Type 2 socket. CCS 2.0 enables charging currents of up to 350 kW.

High power charging stations or ultra fast charging stations can provide charging currents of 150 to 350 kW. These charging stations work with voltages of up to 1000 volts and offer charging currents of up to 500 amps. However, the actual usable charging power ultimately depends on the electric vehicle. Since 2019, the network of high-power charging stations has grown rapidly along the motorways and increasingly in the cities. There are now numerous vehicles on the market that can accept between 100 and 270 kW of charging current.

Hybrid vehicles use at least two different propulsion technologies and have separate energy storage systems, such as an internal combustion engine and an electric motor. These technologies can operate either independently or in combination to power the vehicle.

The unit kilowatt (kW) describes the electrical power, which is defined by the product of voltage (volts) and current (amperes). For electric cars, it can be used to quantify both the drive power of the vehicle and the charging power. However, conversion into the unit of horsepower, which is common for combustion engines, remains possible: 1 kW corresponds to 1.36 hp.

The unit for measuring electrical work is the kilowatt hour (kWh). In the field of electromobility, the energy content of the drive battery is also specified in kilowatt hours. The electricity consumption of the vehicle is therefore stated in kWh per 100 kilometres.

A distinction is made between public and private charging infrastructure. Private charging facilities are only accessible to a limited group of users, such as at home or in a company. Public charging infrastructure, on the other hand, is generally available to the public and must comply with the minimum technical requirements for safe and interoperable installation and operation of the charging pole ordinance.

The charging curve describes the course of the charging power as a function of the battery's state of charge. The charging curve is particularly important for fast charging on long distances, as the battery management system reduces the charging power as the charge level increases. The higher and more even the DC charging curve, the better an electric car is suited for long distances.

The charging power refers to the electrical power in kilowatts (kW) used to charge a traction battery. When this power is multiplied by the charging time, the result is the energy stored in the battery in kilowatt hours (kWh). When charging with alternating current (AC), the charging power normally remains constant and is only reduced shortly before the end of the charging process. However, when charging with direct current (DC), the charging power varies depending on factors such as the state of charge, the temperature of the battery and other factors.

Charging points can be described as the filling stations of electromobility, where electric vehicles can be charged with alternating or direct current (AC/DC).

There are two ways to charge a car: via alternating current (AC) or via direct current (DC). In Europe, the Type 2 plug for AC charging and the CCS plug for DC charging are standard. Public AC charging points always have a Type 2 charging socket. If the vehicle has an older Type 1 connector, appropriate adapter cables are available. Some vehicles also still have the Japanese standard Chademo for fast charging. However, no adapter is available to charge vehicles with a Chademo connection at CCS stations.

Currently, the lithium-ion battery is the most common energy storage device for electric cars because it has a higher energy density than earlier models and does not suffer from the memory effect. The memory effect occurs when the battery is repeatedly not fully discharged and recharged, which can cause its capacity to decrease over time.

The charging cable for the household socket, which is often supplied as an accessory of an electric vehicle, is called an emergency charging cable. The technical term for this is In-Cable Control and Protection Device (IC-CPD) or formerly also In-Cable Control Box (ICCB).

Although electric vehicles actually have no direct CO₂ emissions and are often claimed by manufacturers to be 0 g/km, this claim is often accompanied by the phrase "locally emission-free". This is because emissions can occur for the electricity generation that powers the electric motor. However, with the increasing use of renewable energy sources for power generation, the eco-balance of electric vehicles is improving.

Similar to a full hybrid, a plug-in hybrid also has an electric motor and a combustion engine working together. This allows the plug-in hybrid to recover braking energy while driving and use it again later (recuperation). Unlike a full hybrid, however, the battery of a plug-in hybrid can also be charged during standstill via a plug like a purely electric vehicle and thus store more energy. This means that plug-in hybrids have a greater purely electric range than full hybrids, for example.

The range extender (REX) is a small petrol engine that generates electricity for the electric motor via a generator when the traction battery is empty. This means that in an emergency, one is independent of a charging station for a certain distance and can continue driving even though the battery is empty. However, the use of REX technology is very rare nowadays.

The range of an electric car indicates how far it can travel on a single charge. However, the range varies greatly depending on the individual driving style. Manufacturers usually give values for moderate driving and under optimal climatic conditions.

Recuperation describes the recovery of braking energy. In contrast to an internal combustion engine, which converts kinetic energy into heat that cannot be used further during a braking process, an electric car - whether as a hybrid or full electric - can feed this energy back into the battery as electricity. Here, the electric motor acts like a generator and produces electricity.

Fast charging refers to charging with charging powers of more than 22 kW and is usually carried out with direct current.

The battery charge level is often abbreviated as SoC, which stands for "State of Charge". The SoC is usually given as a percentage.

A traction battery, also known as a drive battery or high-voltage storage battery, is a type of accumulator usually used to supply electrical energy to electric motors in electric vehicles. The battery consists of a series of parallel and serially connected accumulator cells or cell blocks that provide the required voltage and capacity.

The consumption of electric cars is given in kilowatt hours per 100 kilometres. The manufacturers' specifications are based on the WLTP cycle, a standardised test procedure for consumption that is also used for combustion engines. However, the actual consumption is highly dependent on the individual driving profile and external influences.

In principle, it is possible to charge any electric car using a conventional household socket. However, due to the extremely long charging times and the fact that sockets are not designed for continuous loads, it is advisable to install a wallbox. Another advantage of the wallbox is that the charging losses are significantly lower than with an earthed socket (Schuko). A wallbox is a type of private charging station that is usually operated with three-phase current. The charging capacity of a current wallbox can range between 11 and 22 kW, depending on the amperage, whereby models with a charging capacity of more than 11 kW are subject to approval. The plugs and cables of wallboxes are designed for high power and continuous loads. Modern models also offer intelligent functions such as automated charging with surplus electricity from photovoltaic systems.

The Worldwide Harmonised Light Vehicles Test Procedure (WLTP) is a standardised test cycle for measuring the fuel or electricity consumption of vehicles. Electric car manufacturers often use the results of the WLTP test to determine the range of their vehicles. However, the actual ranges in reality, especially at low temperatures, are usually significantly lower than the theoretical values.