A Battery Management System (BMS) is essential for improving the performance, safety, and lifespan of rechargeable battery systems. This project presents the design and implementation of a Battery Management System with active cell balancing using a PIC Microcontroller. The system is developed to monitor and manage three 4V rechargeable batteries connected in parallel. The microcontroller continuously measures the individual voltage of each battery and displays the real-time voltage values on an LCD screen. Three switches are provided to manually isolate each battery from the system, allowing the user to selectively disconnect any battery if its voltage differs from the others. When a particular switch is turned OFF, the corresponding battery is disconnected, and the remaining batteries continue to operate together. This helps in identifying weak or faulty batteries and maintaining system reliability. The system also includes three relays to control the individual charging paths of the batteries. Each relay is activated by the microcontroller to charge a specific battery when required. The LCD display shows the voltage of each battery and their connection status, enabling easy monitoring by the user. Active balancing is achieved by transferring energy from higher-voltage batteries to lower-voltage batteries. Based on the voltage values displayed on the LCD, the user manually isolates the higher-voltage battery using the switch so that the remaining batteries can equalize their energy levels. This process helps maintain uniform voltage distribution among the batteries. The proposed system provides an effective method for battery monitoring, protection, and balancing. It improves battery efficiency, prevents overcharging or deep discharge, and increases the overall lifespan of the battery pack. This design can be applied in small battery-powered systems, portable electronics, and energy storage applications.

The major building blocks of this project are:

• Regulated power supply
• PIC Microcontroller.
• Voltage sensors.
• Three batteries.
• Three Relays.
• Three switches.
• Charging Circuit.
• LCD display.
• LED Indicators
• Crystal oscillator
• Reset button.

Software’s used:

• PIC-C compiler for Embedded C programming.
• PIC kit 2 programmer for dumping code into Micro controller.
• Express SCH for Circuit design.

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