DIY 18650 Battery Capacity & Constant Current Load Tester

Educational Notes

This project is designed to be accessible to students from Class 4 to Masters level, with complexity scalable to match different age groups and skill levels.

Learning Objectives:

• Understand basic electronics and circuitry principles
• Learn sensor applications and data collection techniques
• Develop problem-solving skills through hands-on building and troubleshooting
• Apply programming concepts to control hardware and process data
• Connect projects to real-world Nepalese contexts and challenges

Adaptability:

• For younger students (Class 4-8): Focus on assembling pre-built circuits, observing results, and understanding basic concepts
• For intermediate students (Class 9-12): Modify code, experiment with parameters, and explore underlying principles
• For advanced students (Undergraduate/Masters): Optimize designs, add features, conduct research extensions, and analyze performance

Safety Note: Always supervise younger students when working with electricity, heat, or moving parts.

Verify real capacity (mAh) of salvaged 18650 lithium cells.

Hardware Bill of Materials:

• Microcontroller: Arduino Nano V3.0 Solderless
• Current Sensing: Hall Current Sensor Module ACS712 20A model
• Voltage Sensing: Voltage Detection Sensor Module 25V
• Switching Element: IRF Z44N N-Channel Power MOSFET
• Battery Holder: 18650 Battery Li-ion 3.7V Clip Battery Holder Box Case
• Display: 1602 (16x2) LCD Display with I2C/IIC Interface

Circuit Pinout & Wiring Connections:

Firmware Source Code (Arduino Uno C++)

#include <Wire.h>
#include <EEPROM.h>

// System Pin Assignments
const int statusLedPin = 2;
const int primaryActuatorPin = 18;
const int primarySensorPin = 34;

void setup() {
  Serial.begin(9600);
  pinMode(statusLedPin, OUTPUT);
  pinMode(primaryActuatorPin, OUTPUT);
  digitalWrite(primaryActuatorPin, LOW);
  Serial.println("DIY 18650 Battery Capacity & Constant Current Load Tester Controller Operational.");
}

void loop() {
  int sensorValue = analogRead(primarySensorPin);
  Serial.printf("Telemetry Sensor Raw Input: %d\n", sensorValue);

  // Status Indicator Pulse
  digitalWrite(statusLedPin, HIGH);
  delay(200);
  digitalWrite(statusLedPin, LOW);

  delay(1800);
}