Press Release 148/2018

Turbocharging E-Bikes

Easier, Faster, Further: The Performance of E-Bike Motors Does Not Get Close to That of Other Electric Vehicles – Engineers at KIT Want to “Pimp” the Electric Bikes
2018_148_Forscher bringen E-Bikes auf Touren_72dpi
Researchers at KIT are testing e-bikes on a test bench commonly used in the automotive industry. (Photo: Markus Breig, KIT)

E-bikes are all the rage. However, their drives have often been optimized more with regard to costs and less with regard to best possible power delivery. Compared to other electrically powered vehicles, pedelecs therefore often perform poorly in terms of efficiency and range. Researchers at Karlsruhe Institute of Technology (KIT) now want to improve e-bikes and have set up a special test bench for it.


“Most motors that are now installed in e-bikes were originally developed as drives for other small electrical devices, for example for power steering in cars,” says Martin Doppelbauer from the Institute of Electrical Engineering (ETI) at KIT. That’s why they are not bad per se, but have also not really been optimized for providing the best performance, according to the Professor for Hybrid Electric Vehicles. An average electric car currently has an efficiency of 90 percent. So the energy supplied is converted almost completely into output. “In conventional pedelecs, on the other hand, it’s only 70 percent,” says Doppelbauer. Future motors need to be particularly more compact, and therefore smaller and lighter with a greater range. To achieve this, researchers at ETI are using development methods and findings from larger drives for battery electric vehicles that are already highly developed and applying them to small pedelec motors.


However, not only the motor itself has still room for improvement but also components such as gears, cooling, power electronics and not least the battery. “So far most manufacturers don’t offer a quick charge system,” says Doppelbauer. ETI is now developing one together with a Heidelberg e-bike manufacturer. “City bikes need to be chargeable in half an hour while shopping, then batteries can be made smaller, lighter and therefore more practical.”


To put the new developments through their paces, the ETI researchers have set up a new test bench which is commonly used in the automotive industry. “Here we can perform fully automatic and realistic endurance tests on bikes,” explains Doppelbauer. The bikes will go through different cycles at all speeds, and ascents and descents can also be simulated, the way it is also done in large motors.


More about the KIT Mobility Systems Center:



Being “The Research University in the Helmholtz Association”, KIT creates and imparts knowledge for the society and the environment. It is the objective to make significant contributions to the global challenges in the fields of energy, mobility, and information. For this, about 10,000 employees cooperate in a broad range of disciplines in natural sciences, engineering sciences, economics, and the humanities and social sciences. KIT prepares its 22,800 students for responsible tasks in society, industry, and science by offering research-based study programs. Innovation efforts at KIT build a bridge between important scientific findings and their application for the benefit of society, economic prosperity, and the preservation of our natural basis of life. KIT is one of the German universities of excellence.

mex, 20.11.2018

Margarete Lehné
Chief Press Officer (acting)
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Dr. Felix Mescoli
Press Officer
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