Introduction

A Battery Level Indicator is an electronic system used to display the remaining charge level of a battery. It helps users know when the battery needs recharging or replacement, thereby preventing sudden power failure and extending battery life.

Battery level indicators are widely used in UPS systems, inverters, mobile devices, electric vehicles, and portable electronics.

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Objective of the Project

The main objectives of this project are:

• To monitor the battery voltage level.
• To indicate battery charge status visually using LEDs.
• To prevent deep discharge of batteries.
• To understand voltage measurement and comparison techniques.

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Working Principle

The battery level indicator works by comparing battery voltage with predefined reference levels.

Basic Method (Comparator Based)

• The battery voltage is divided using a resistor network.
• Each voltage level is compared using transistors or comparator ICs.
• When a specific voltage level is reached, the corresponding LED turns ON.
• Multiple LEDs indicate different battery levels (Low, Medium, High, Full).

Arduino-Based Method

• Arduino continuously reads battery voltage using an analog pin.
• The voltage is mapped to battery percentage.
• LEDs or a display show the battery status.

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Components Required

Basic Battery Level Indicator

• Battery (9V / 12V)
• LEDs (4 or 5)
• Resistors (220Ω, voltage divider resistors)
• Transistors (BC547) or Comparator IC (LM339)
• Breadboard & wires

Arduino-Based Battery Level Indicator

• Arduino Uno
• Battery
• Voltage divider resistors
• LEDs
• Jumper wires

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Circuit Diagram

Basic Circuit (LED Indicator)

Battery +
   |
 [Voltage Divider]
   |
 Comparator / Transistor
   |
 LED + 220Ω
   |
 GND

Each comparator output controls one LED representing a battery level.

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Arduino-Based Circuit

Battery + ---- R1 ---- A0 ---- R2 ---- GND
LEDs --------- Arduino D8–D11
GND ---------- Common Ground

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Arduino Code for Battery Level Indicator

int batteryPin = A0;
int ledLow = 8;
int ledMid = 9;
int ledHigh = 10;
int ledFull = 11;

void setup() {
  pinMode(ledLow, OUTPUT);
  pinMode(ledMid, OUTPUT);
  pinMode(ledHigh, OUTPUT);
  pinMode(ledFull, OUTPUT);
}

void loop() {
  int sensorValue = analogRead(batteryPin);
  float voltage = sensorValue * (5.0 / 1023.0) * 3; // Voltage divider factor

  digitalWrite(ledLow, voltage > 9.5 ? HIGH : LOW);
  digitalWrite(ledMid, voltage > 10.5 ? HIGH : LOW);
  digitalWrite(ledHigh, voltage > 11.5 ? HIGH : LOW);
  digitalWrite(ledFull, voltage > 12.5 ? HIGH : LOW);

  delay(500);
}

Code Explanation

• Arduino reads battery voltage via a voltage divider.
• The voltage is converted into real voltage.
• LEDs indicate battery level based on voltage thresholds.

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Advantages

• Prevents battery over-discharge
• Easy battery monitoring
• Simple and low-cost
• Improves battery life

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Applications

• Inverters and UPS systems
• Electric vehicles
• Portable electronic devices
• Solar power systems
• Battery-operated gadgets

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Conclusion

The Battery Level Indicator is a practical and essential electronics project that helps monitor battery health and charge status. It improves reliability and prevents unexpected power loss. This project can be further enhanced using LCD displays, IoT monitoring, or mobile app integration.