Self-sufficient hybrids are available:

• Mild hybrid
  Electric motor 10...15 kW (battery approx. 1 kWh) as starter and generator to support the combustion engine during acceleration (boosting), works as a generator during regenerative braking (recuperation), with automatic start-stop system. Energy/fuel savings of 15-20 %
• Full hybrid
  E-motor > 15 kW (battery approx. 2 kWh) supports the VM in addition to all operating modes of the mild hybrid so that it can also move the vehicle on its own, for example in city traffic or when maneuvering. Fuel saving approx. 40 %
• Plug-in hybrid
  (plug-in hybrid) The full hybrid variant is mainly electric (engine output 50 kW, battery approx. 15 kWh). When stationary, it is charged/recharged at the socket (plug-in). If the energy content of the battery is no longer sufficient after a longer period of driving, the VM is automatically activated (range extender).

Torque-speed curve (tendency) (maximum torque of the EM already at zero speed)

If an energy management system optimizes the work of the generator, starter and battery and the vehicle has an automatic start-stop system, this equipment is referred to as a micro-hybrid (fuel savings of 5-10%, not a true hybrid due to the lack of a second drive).

In addition to the electric drive and the control electronics with bus system, all genuine hybrids have a high-voltage on-board electrical system with new safety requirements.

The emission-free e-vehicle is moved exclusively by the battery-powered electric motor (>< 30 kW), which is operated both by the motor and the generator. The battery (approx. 30 kWh) allows long-distance travel. All systems are capable of recuperation. Electric braking relieves the mechanical brakes and protects the environment with less tire wear.

System structure
In the parallel hybrid, both motors move the vehicle axle (autonomous operation is possible). It can even be designed as an all-wheel drive system with more than two motors. The addition of the torques allows their cost- and weight-saving dimensioning. Design for purely electric operation is possible. In the case of the serial hybrid, which corresponds to the diesel-electric drive, the EM supplies the entire torque. The combustion engine, which has no mechanical connection to the driven vehicle axle, moves the electric generator, which produces the drive energy for the engine supply or fills the drive battery, which can also be charged from the mains. It can also briefly supply additional power for higher power requirements. Plug-in, full hybrids use this structure.

E-vehicle drive with performance-enhancing, hybrid supply storage (TUD, Chair of EMA, Dipl.-Ing. Arne Brix).

Mixed hybrids automatically and variably combine both structures using a special gearbox depending on the driving conditions. Either the VM only charges the battery via the generator, which feeds the EM (serial hybrid), and/or it is mechanically coupled to the drive shaft (parallel hybrid). The core of the e-vehicle corresponds to an autonomous drive, the Power Drive System PDS according to EN 61800 with the working machine vehicle, as the motion cell of a mechatronic system.

Components
In addition to the bus-coupled IE, the most important vehicle components include motors and storage units. Together with the charging infrastructure, they determine efficiency and range. The asynchronous, synchronous and reluctance motors used have the advantageous torque curve in common. Lithium-ion systems (Li-ion, lithium-polymer), but also nickel-cadmium, nickel-metal hydride or nickel-zinc, lead-acid batteries and high-temperature sodium-nickel chloride collectors (for serial concepts) are used as long-life batteries with high power density and high energy content (range 300 - approx. 500 km, 33-60 kWh). Power electronic components (inverters, rectifiers, frequency converters, DC/DC converters) play a decisive role in enabling the bidirectional flow of energy and linking the classic low-voltage (12 V) and high-voltage (150 - ≤ 600 V) networks. Such components lead to completely different accident risks (battery fire, contact with the high-current cable).

Environmental balance
Hybrid and electric vehicles are sustainably emission-free if green electricity is used for production and operation.

Outlook
The triumph of e-mobility seems certain, provided that the inadequate charging infrastructure is replaced by practicable, harmonized, securely communicating systems. For the time being, this path is focused on passenger cars and public transport. It is supported by hydrogen and fuel cell technology as well as SuperCaps(http://www.cleanenergypartnership.de). In addition to private transport (including two-wheelers), the move away from VM is also reaching commercial vehicles and ships. Trucks with energy supply from overhead lines are just as much a case in point as long-distance/local bus systems. They are recharged from conductive high-current charging stations installed along the route as well as inductive fast charging stations at stops. The resulting smaller battery dimensions (weight, space) allow a greater range. The scarce raw material Li must be replaced in the long term. Alternatives such as Na, S, Si, Mn, Al, Zn are therefore being tested.

The future will also be determined by assistance systems through to automated or autonomous driving with clarification of liability/data protection. Fully electric car-sharing and robot vehicles will limit individual traffic. Permissible grid feedback must be ensured.

Dr.-Ing. habil. Joachim Krause

Recuperation
Conversion of mechanical kinetic energy into electrical energy during braking, downhill driving, etc. The electric motor works as a generator that feeds this energy into the battery.