Challenges and Solutions for Range Extenders - From Concept Considerations to Practical Experiences 2011-37-0019
For a broad acceptance of electric vehicles, the trade-off between all electric range and battery cost respectively weight represents the most important challenge. The all electric range obtained under real world conditions most often deviates significantly from the nominal value which is measured under idealized conditions. Under extreme conditions - slow traffic and demanding requirements for cabin heating or cooling - the electrical range might become less a question of spatial distance but even more of total operation time.
Whereas with conventional powertrain, high flexibility of the total driving range can be obtained without sacrificing cost, with a pure battery vehicle this results in extreme high cost and weight of the energy storage. Therefore the difference between the typical daily driving range (e.g. in Germany 80-90% is below 50 km) and the minimum total range requested by most customers for acceptance of battery vehicles (200- 250 km), becomes essential. Based on the current battery technology, the most attractive approach is a battery capacity designed for the typical daily driving distance (e.g. 50 km) and an ICE powered Range Extender, covering larger energy requirements (higher power demand or longer driving distances).
The most effective technical solution for such a Range Extender is largely determined by the ratio between pure battery operation and vehicle operation supported by the ICE. With primarily battery driven vehicles, the priorities for the ICE have to be set completely different compared to the conventional powertrain: NVH, package and weight are the most important items whereas the efficiency of the ICE is less important due to the low share of ICE operation. Hence, even ICE concepts, which are not optimal for pure ICE driven powertrains, proving to be ideal ICE for this kind of Range Extender application.
For lowest cost and best fuel economy AVL developed a Range Extender solution with a unique 2-cylinder piston engine based on a cost and friction optimized design originating from 2-wheelers.
With focus on best NVH, packaging and weight, an extremely compact and low weight Range Extender unit based on a highly integrated combination of a Rotary engine and an electric generator, was developed which also convinces with an outstanding NVH performance. This makes Range Extender solutions essential enablers for an affordable electric mobility.