Fraunhofer Institute for Transportation and Infrastructure Systems IVI
How operating and charging strategies affect the range, costs, and sustainability of electric buses—and what advantages are created for transport companies.
More and more transport companies are turning to battery-electric buses to make their fleets climate-neutral. However, high acquisition costs, limited ranges, and restrictions on regarding times are presenting new challenges for public transport providers. In a recent study, the Fraunhofer Institute for Transportation and Infrastructure Systems IVI evaluated the energy consumption and charging behavior of an urban electric bus fleet over a period of more than two years. The study shows that targeted adjustments in operation and charging management can reduce energy consumption, extend battery life, and significantly lower CO₂ emissions without requiring any major changes to operating procedures.
Energy efficiency depends on temperature and speed
Based on real operating data, the study presents an analysis of the energy consumption of electric buses as a function of outside temperature and average driving speed. Clear reference values were derived for typical urban route cycles. These key figures provide transport companies with a reliable basis on which to forecast ranges accurately, plan routes realistically, and schedule charging windows appropriately.
Longer service life through intelligent charging strategies
In order to derive recommendations for battery-friendly use, the focus was put on the state of charge (SOC) window during operation and in idle phases, as well as the charging power. Charging and battery management offer significant potential for optimization: If buses are not kept in a permanent 95-100% SOC range, but are operated in an SOC window reduced by around 20 percentage points, battery aging can be slowed down considerably. An even greater effect can be achieved by implementing intelligent depot charging: Buses should only be charged to full capacity shortly before their next use, rather than being parked for long periods in a fully charged state. Simulations show that this can extend battery life from around 11 to up to 16 years – without any significant delays in operation.
For practical implementation, the research team recommends the use of 90th percentile consumption curves. These not only represent average values, but also take into account peak loads under unfavorable conditions. This allows charging and deployment schedules to be adjusted according to temperature and speed, thereby specifically controlling energy efficiency, reliability, and battery life.
Practical research for operation
What makes this data particularly relevant: All results are based on long-term monitoring data from an urban e-bus fleet in real-life operation. Transport companies thus receive not theoretical models, but reliable, field-tested recommendations for action. This makes the results directly applicable – both for optimizing existing fleets and for planning new infrastructure.
Since the numbers given are to be understood as cycle-specific energy consumption for urban driving cycles, there are further opportunities for investigation and validation with different usage profiles, e.g., for intercity lines or in logistics.
The complete results have been published in the World Electric Vehicle Journal as an open access paper.