Design of Adaptive Multiport Charging System for Electric Motorcycle Batteries

Abstract

The increasing adoption of electric motorcycles requires charging infrastructure that is flexible, adaptive, and capable of simultaneously accommodating battery packs with different voltage classes. This paper proposes an adaptive multiport DC-DC charging system consisting of three independent buck-converter ports connected to a common DC bus. The ports are designed to charge 31-Ah LiFePO4 battery packs in the 48-V, 60-V, and 72-V classes. Each port independently implements a proportional-integral-controller-based Constant Current-Constant Voltage (CC-CV) charging strategy. The charging-current reference is adaptively determined using a two-dimensional C-rate lookup table based on the battery State of Charge (SoC) and temperature and is subsequently scaled according to the battery-pack capacity. Meanwhile, the charging-voltage reference is selected according to the identified battery voltage class. The controller operates in CC mode when the SoC is below 80% and automatically switches to CV mode when the threshold is reached. To reduce thermal stress, the charging-current reference is progressively reduced at elevated temperatures, and charging is disabled at 60 °C. MATLAB/Simulink R2024a simulation results show that the proposed reference generator produces charging currents of 31 A, 24.8 A, 6.2 A, and 0 A under the evaluated operating conditions. The results also demonstrate that all three ports can independently track their current and voltage references and perform automatic CC-CV transitions during simultaneous charging. These findings demonstrate the feasibility of the proposed system as a flexible charging platform for electric motorcycle batteries with different voltage classes.