This paper presents a hybrid battery monitoring and charging system for autonomous marine vessels, integrating photovoltaic (PV) modules with a hydrodynamic impeller. The system addresses limitations of conventional engine-dependent charging by harvesting solar energy during idling and hydropower from water flow during vessel motion. A microcontroller monitors battery voltage, current, and temperature, implementing a smart switching algorithm to select the optimal charging source dynamically. Protection features including overcharge prevention, deep discharge cutoff, and thermal regulation enhance battery lifespan. Real-time operational parameters are displayed for user awareness. This dual-mode approach minimizes fossil fuel dependency, ensuring reliable power for navigation, propulsion, and communication systems. The proposed solution is ideal for fishing vessels, autonomous robots, and small transport boats requiring sustainable and self-sufficient power management.