With the increasing reliance on battery-powered systems in renewable energy and portable electronics, there is a growing need for real-time monitoring to ensure performance, safety, and reliability. The Real-Time Battery Monitoring System using an OLED display is a compact, user-friendly solution developed to provide continuous and clear feedback about a 3.7V Li-ion battery used in solar or portable applications.

This system is designed to monitor the battery’s voltage, current, and charging status, while also displaying a real-time clock (RTC) to track how long the system has been charging or running. The collected data is visually represented on a 0.96-inch OLED screen, making it ideal for off-grid use, solar lighting systems, or any portable energy unit where live status feedback is valuable.

The core of the system is an ESP32 microcontroller, which handles sensor readings, timekeeping, and display control. A voltage divider circuit is used to safely measure the 3.7V battery voltage through an analog input. The battery current is measured using an INA219 sensor, which accurately reads the current flowing into or out of the battery. These two parameters — voltage and current — help estimate the charging or discharging condition of the battery in real time.

To enhance user interaction, the system includes an OLED display that shows:

• Battery Voltage (e.g., 3.8V)
• Battery Condition (e.g., Charging, Discharging, Low Battery)
• Current Flow (e.g., +0.50A when charging, -0.20A when discharging)
• Elapsed Time since system startup or charging began

The battery condition is determined using thresholds:

• >4.1V → Fully Charged
• 3.7–4.1V → Charging/Good
• 3.3–3.6V → Low Battery