The increasing popularity of e-bikes, especially pedelecs, has led to a growing interest in consideration of e-bike cycling. To achieve a deeper understanding on the process of e-bike cycling and in particular the effects on the rider it can be instrumental to use simulation methods. In this context, the e-bike drive system and its function are of central importance for e-bikes. Therefore, this work proposes a functional modeling of the powertrain of an e-bike with a mid-drive motor, considering legal constraints and support functionalities. The model incorporates the mechanical transmission between pedals, motor, and crank shaft, allowing for a detailed analysis of the e-bike’s performance. Additionally, the support mechanism is depicted, where an electric motor amplifies the rider’s pedaling torque. The electrical behavior of the motor, energy consumption, and battery state of charge are also integrated into the model. This comprehensive approach aims to provide a generic representation of e-bike systems, considering real-world functionalities and constraints. The generic model structure also allows to achieve a modularity of sub-models to consider different level of detail. This is demonstrated by implementing a simplified and a detailed model of the battery, which allows an evaluation of the simplified approach. Finally, measurements of a real e-bike system are used to evaluate the model of the e-bike system. These serve as an input for the simulation so that the results calculated by the model can be compared with real-world data.