Efficient and safe charging of lithium-ion batteries is essential for maximizing their lifespan and performance. This paper presents the design and implementation of a microcontroller-based Li-ion battery charger that employs real-time monitoring, adaptive charging strategies, and built-in safety mechanisms. The system integrates a CC/CV charging approach with automatic current regulation, overcharge protection, and reverse polarity detection. A current sensor module ensures continuous monitoring, while an LCD interface provides real-time feedback on charging parameters. Experimental validation was conducted using multiple Li-ion cells in various conditions, like new, aged, and deeply discharged, to evaluate charging behavior and safety under different scenarios. The system successfully regulated current and voltage, managed preconditioning for low-voltage cells, and transitioned smoothly between charging phases. A key contribution of this work is the development of a low-cost, microcontroller-based platform that enables flexible implementation and testing of diverse charging strategies. Its open-source architecture and modular design make it highly suitable for research, educational use, and experimental development in battery management systems. Future enhancements may include the integration of adaptive algorithms based on internal resistance and temperature, enabling smarter and more efficient charging.

An important element in communications systems is the router. The paper proposes a remote temperature monitoring system for it. This was implemented based on Arduino Uno development platform. In addition, an Android user-friendly interface has been created; it can be installed on a smart terminal (phone or tablet) and its role is to display the router temperature and to notify the user if it has exceeded a maximum set value. There are two methods of notifications: one is using different colors for the displayed temperatures and the other using an alert. The temperature is measured with a sensor and the data is then processed by the microcontroller and sent to the Bluetooth module using serial interface. Also, the measured values can be seen on an LCD display. The hardware, software designs and the simulation and experimental results of the proposed system are presented.