How To Make Battery Capacity Tester

Nowadays fake Lithium and NiMH batteries are everywhere which is sold by advertising with higher capacities than their true capacity. So it is really difficult to distinguish between a real and a fake battery. Similarly, it is difficult to know the capacity retained in the salvaged 18650 laptop batteries. So, a device is required to measure the true capacity of the batteries.

Diagram:

Code:

#include<JC_Button.h>
#include <Adafruit_SSD1306.h>

#define SCREEN_WIDTH 128 // OLED display width, in pixels
#define SCREEN_HEIGHT 64 // OLED display height, in pixels

// Declaration for an SSD1306 display connected to I2C (SDA, SCL pins)
#define OLED_RESET     4 // Reset pin # (or -1 if sharing Arduino reset pin)
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);


const float Low_BAT_level = 3.0;
//Current steps with a 3R load (R7)
const int Current [] = {0,100,200,300,400,500,600,700,800,900,1000};
const byte PWM_Pin = 10;
const byte Buzzer = 9;
const int BAT_Pin = A1;
int PWM_Value = 0;
unsigned long Capacity = 0;
int ADC_Value = 0;
float Vcc = 4.28; // Voltage of Arduino 5V pin ( Mesured by Multimeter )
float BAT_Voltage = 0;
float sample =0;
byte Hour = 0, Minute = 0, Second = 0;
bool calc = false, Done = false;
Button UP_Button(2, 25, false, true);
Button Down_Button(3, 25, false, true);


void setup () {
//
Serial.begin(9600);
pinMode(PWM_Pin, OUTPUT);
pinMode(Buzzer, OUTPUT);
analogWrite(PWM_Pin, PWM_Value);
UP_Button.begin();
Down_Button.begin();
display.begin(SSD1306_SWITCHCAPVCC, 0x3C);
display.clearDisplay();
display.setTextColor(WHITE); 
display.setTextSize(2);
display.setCursor(12,25);
display.print("EASY TECH");
display.display();  
delay(2000);
display.clearDisplay();
display.setTextSize(2);
display.setCursor(2,15);
display.print("Adj Curr:"); 
display.setCursor(2,40);
display.print("UP/Down:");
display.print("0");
display.display();  
}

//************************* End of Setup function *******************************

void loop() {
  UP_Button.read();
  Down_Button.read();
if (UP_Button.wasReleased() && PWM_Value < 256 && calc == false)
 {
  PWM_Value = PWM_Value + 25; 
  if(PWM_Value > 256){
    PWM_Value=PWM_Value-25;
  }
  analogWrite(PWM_Pin,PWM_Value);
  display.clearDisplay();
  display.setCursor(2,25);
  display.print("Curr:");   
  display.print(String(Current[PWM_Value / 25])+"mA");
  display.display();  
  Serial.println(String(Current[PWM_Value / 25]));
  Serial.print(PWM_Value);
 }
if (Down_Button.wasReleased() && PWM_Value > 1 && calc == false)
{ 
  PWM_Value = PWM_Value - 25; 
  analogWrite(PWM_Pin,PWM_Value); 
  display.clearDisplay();
  display.setCursor(2,25);
  display.print("Curr:");   
  display.print(String(Current[PWM_Value / 25])+"mA");
  display.display();  
  Serial.println(String(Current[PWM_Value / 25]) + "mA");
  
} 

if (UP_Button.pressedFor (1000) && calc == false)
{
  digitalWrite(Buzzer, HIGH);
  delay(100);
  digitalWrite(Buzzer, LOW);
  display.clearDisplay();
  timerInterrupt(); 
   
  }
}

//************************* End of Loop function *******************************

void timerInterrupt(){
  calc = true;
  while (Done == false)  {
     Second ++;
    if (Second == 60)  {
      Second = 0;
      Minute ++;      
    }
    if (Minute == 60)  {
      Minute = 0;
      Hour ++;
    }

 //************ Measuring Battery Voltage ***********
  
  for(int i=0;i< 100;i++)
  {
   sample=sample+analogRead(BAT_Pin); //read the Battery voltage 
   delay (2);
  }
  sample=sample/100; 
  BAT_Voltage = sample * Vcc/ 1024.0; 
 
  //*********************************************

    display.clearDisplay();
    display.setTextSize(2);
    display.setCursor(20,5);
    display.print(String(Hour) + ":" + String(Minute) + ":" + String(Second));

    display.setTextSize(1);
    display.setCursor(0,25);
    display.print("Disch Curr: ");   
    display.print(String(Current[PWM_Value / 25])+"mA");
     
    
    display.setCursor(2,40);   
    display.print("Bat Volt:" + String(BAT_Voltage)+"V" );



    Capacity =  (Hour * 3600) + (Minute * 60) + Second;
    Capacity = (Capacity * Current[PWM_Value / 25]) / 3600;
    display.setCursor(2, 55);
    display.print("Capacity:" + String(Capacity) + "mAh");
    display.display();

    
    if (BAT_Voltage < Low_BAT_level)
    {
      Capacity =  (Hour * 3600) + (Minute * 60) + Second;
      Capacity = (Capacity * Current[PWM_Value / 25]) / 3600;
      display.clearDisplay(); 
      display.setTextSize(2);      
      display.setCursor(2,15);     
      display.print("Capacity:");
      display.setCursor(2,40);  
      display.print(String(Capacity) + "mAh");
      display.display();
      Done = true;
      PWM_Value = 0;
      analogWrite(PWM_Pin, PWM_Value);
      digitalWrite(Buzzer, HIGH);
      delay(100);
      digitalWrite(Buzzer, LOW);
      delay(100);
      digitalWrite(Buzzer, HIGH);
      delay(100);
      digitalWrite(Buzzer, LOW);
      delay(100);
    }
       delay(1000);
  } 
   
}