Which is a better powertrain

The hybrid drive: on the move with two systems

A hybrid drive is the combination of different drive principles or energy sources. Common are hybrids with gasoline and gas drives (natural gas or LPG) as well as with gasoline or diesel and electric drives. We have summarized the most important points for the latter.

Technology and the environment

The basic idea behind gasoline / diesel-electric hybrid vehicles is to combine the advantages of the electric and the combustion engine in such a way that the overall system works as efficiently and with a high degree of efficiency as possible. Excess power from the internal combustion engine is converted into electrical energy and stored in a battery. The latter in turn feeds the electric motor when required. This is energetically sensible as long as the efficiency improvements exceed the losses from the conversion of mechanical into electrical energy and its storage in a battery. In addition, the kinetic energy released during braking can be stored in the battery and used for propulsion. If the battery power drops, the electric motor automatically works as a generator and recharges the battery while driving. In order to optimally utilize the advantages of the two drives and to compensate for the disadvantages, the optimal operating mode is automatically selected permanently.

Advantages: lower fuel consumption and better acceleration

In order to get the same driving performance as a vehicle equipped only with an internal combustion engine, a smaller internal combustion engine is usually sufficient when combining an internal combustion engine and an electric motor (“downsizing”). The latter is also regulated so that it always works with optimum efficiency. The generator uses excess energy to charge the battery. When braking, energy is also recovered and fed into the battery. Fuel savings of around 15 to 25 percent are possible - depending on the design of the system - compared to a conventional gasoline vehicle of the same order of magnitude.

In contrast to the internal combustion engine, which only reaches its maximum torque in the upper third of the speed range, the electric motor can do this from a standing start. The combination of a combustion engine and an electric motor enables the vehicle to be accelerated around 10 to 20 percent faster.

Differences between mild hybrid and full hybrid

Mild hybrid

On the one hand, a combined starter-generator generates electricity when coasting and braking, which is stored in a battery, and on the other hand, as an electric motor, supports the internal combustion engine when required.

Example: Honda Integrated Motor Assist System (IMA)
Honda's Integrated Motor Assist System (IMA) stores the energy that is normally lost when braking or decelerating, and then using it again when accelerating. The IMA system always automatically selects the most energy-saving drive variant while driving.

  • Accelerating / overtaking: When accelerating or overtaking, the electric motor supports the petrol engine and thus increases the overall drive power.

  • Normal travel: after cruising speed has been reached, the petrol engine works on its own, while the electric motor in generator mode charges the battery if necessary.

  • Decelerating / downhill: When decelerating or when driving downhill, the electric motor acts as a generator and recharges the battery.

  • Vehicle stop: As soon as the vehicle stops or is idling, the combustion engine is switched off, thereby saving fuel. If the brake is released or the clutch is operated, it starts again immediately.

Full hybrid

Same drive principle as with the mild hybrid. In addition, it is also possible to drive alone with an electric motor up to around 50 km / h (e.g. Toyota Prius). The power of the electric motor used is higher than that of the mild hybrid.

Example: Toyota Hybrid Synergy Drive Technologie (HSD)
HSD technology is designed to optimize performance and efficiency at the same time. It uses the synergy between the electric and petrol drive by automatically selecting the optimal operating mode while driving.

  • Starting off: When starting off and at low speed, the electric motor uses energy from the battery to propel the vehicle. When the battery level is low, the petrol engine starts to charge the battery; also with a cold catalytic converter and with simultaneous use of additional electrical consumers (e.g. air conditioning, heating).

  • Normal driving: In normal driving, the hybrid drive uses both the electric and the gasoline engine. The gasoline engine provides power for the generator, which in turn supplies the electric motor with electricity. At the same time, the petrol engine drives the front wheels via a power switch. The ratio of the force distribution is permanently monitored and always regulated in such a way that maximum efficiency is guaranteed.

  • Accelerating / overtaking: For acceleration or overtaking maneuvers that require maximum performance, the battery - provided the charge level is sufficient - feeds additional energy into the system to provide effective support for the petrol engine and electric motor.

  • Decelerating / downhill: When decelerating and when driving downhill, the electric motor acts as a generator and recharges the battery.

  • EV mode: If the driver activates the EV driving mode, the vehicle is - if possible (depending on certain parameters such as speed, state of charge of the battery, catalyst temperature) - driven exclusively by its electric motor, which provides the necessary energy draws from the battery and does not consume any fuel.

  • Vehicle stop: as soon as the vehicle stops, the petrol engine is stopped and fuel consumption goes to zero.

Plug-in hybrid and range extender

If the battery for driving the electric motor in a hybrid vehicle can also be charged via the power grid, it is referred to as a plug-in hybrid. Plug-in hybrids have a much more powerful electric motor and a larger high-voltage battery than full hybrids. This means they can drive purely electrically at speeds of over 100 km / h and achieve electric ranges between 30 and 60 kilometers, depending on the battery size and efficiency, and thus preferably drive locally emission-free in cities. Electric vehicles with range extenders also count among the hybrid vehicles, as they use two different energy sources to drive them. Although the direct drive is usually only provided by the electric motor, if the battery charged via the mains is empty, it is charged by an internal combustion engine in order to extend the range.

Plug-in hybrids are particularly suitable when the vehicle is mainly used for journeys within the electric range and can be recharged at the start / destination locations (e.g. for commuters), but are also suitable for long journeys and vacation trips have to be. In order to be able to achieve the highest possible amount of electric driving in everyday life, long-distance assignments should be the exception.

Effects on health and the environment

The hybrid drive shows its advantages especially when driving in the city and in urban surroundings with frequent accelerations and decelerations, since proportionally more energy can be recovered and reused than on motorways. This is reflected in lower pollutant emissions and, in particular, in lower fuel consumption.

Safety and suitability for everyday use


The results of the EuroNCAP crash test show that hybrid vehicles are just as safe as vehicles with conventional drives. The models Honda Insight, Mitsubishi Outlander PHEV, Opel Ampera, Toyota Prius and Volvo V60 D6 Hybrid achieved five stars in the overall rating. However, right-hand drive models were used when testing the Honda Insight and Toyota Prius. Since the installation of the units in the engine compartment plays an important role, the results of the front crashes (part of the assessment for occupant protection) cannot be fully transferred to the models (left-hand drive) sold in Germany.

Take Toyota Hybrid Synergy Drive Technology (HSD), for example: Toyota's hybrid system switches off all electrical systems immediately in the event of an accident, based on the airbag trigger signal, and interrupts battery contact.

If the airbags are not deployed in minor accidents, there are two options for manual deactivation of the hybrid battery: The high-voltage circuit is also interrupted by removing the maintenance plug or the IGCT relay. It should be noted, however, that after deactivating the hybrid battery, the high voltage (Toyota Prius: 500 volts, Lexus RX450h: 650 volts) is maintained for about three minutes. All high voltage cables are marked orange. The hybrid battery itself is safely housed in the luggage compartment behind the rear seats and is protected by an additional steel structure.

Suitability for everyday use

An ADAC long-term test with a Toyota Prius over 90,000 kilometers has shown that the hybrid technology has also proven itself in everyday life. The Prius ran absolutely flawlessly. No breakdowns, no failures, no extraordinary repairs - neither in the conventional area of ​​the vehicle nor with the hybrid technology and the battery.

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