Sustainable Hybrid Charging System for Educational Electric Vehicles

Abstract

This paper presents the design and validation of a modular, low-cost energy system for the HeliosRover, a solar-powered electric vehicle developed for STEM outreach. The system integrates a custom 4S20P lithium-ion battery pack from recycled 18650 cells, a battery management system, a hybrid solar and grid charging architecture, a centralized charge controller, and a single-axis solar tracker. Subsystem tests verified stable power delivery with voltage deviations within $\pm 0.2 \mathrm{~V}$ and safe operation under continuous charging. The hybrid charging system switched seamlessly between sources, maintaining consistent output with minimal ripple. Solar charging averaged 19.5 V and 4.7 A, while solar tracking improved power capture by 7% and reduced variability. A 48-hour charging test confirmed reliable monitoring and safe termination by the battery management system. Outreach validation at Portland High School demonstrated the system’s value for STEM education. Results confirm sustainability, reliability, and replicability as a robust platform for modular electric vehicles.