// Very simple Arduino Lithium-ion battery capacity 
#include <LiquidCrystal_I2C.h>


#define LED 13
#define rele 8
#define resistor 24
LiquidCrystal_I2C lcd(0x27,16,2);
float capacity=0, value,voltage,current, time=0;
int min;

void measure (void) {

  value= analogRead(0);

  voltage=value/1024*5.0;

  current = voltage/resistor;

  capacity=capacity+current/3600;

  time++;

  Serial.print("Voltage= ");
  Serial.print(voltage);


  Serial.print("V Current= ");
  Serial.print(current);

  Serial.print("A Capacity= ");
  Serial.print(capacity);
  Serial.print("Ah ");

  Serial.print("Discharging time= ");
  Serial.print(time);
  Serial.print("s ");

  Serial.print("\n");
}

boolean x=false;

ISR(TIMER1_OVF_vect) {
  TCNT1=0x0BDC;
  x=!x;

  measure();

};

void setup() {

  pinMode(LED, OUTPUT);

  TIMSK1=0x01; // enabled global and timer overflow interrupt;
  TCCR1A = 0x00; // normal operation page 148 (mode0);
  TCNT1=0x0BDC; // set initial value to remove time error (16bit counter register)
  TCCR1B = 0x04; // start timer/ set clock

  Serial.begin(115200);
  lcd.init();	// initialize the lcd
  // Print a message to the LCD.
  lcd.backlight();
  lcd.setCursor(0,0);
  lcd.print("V=     Ah=");
  lcd.setCursor(0,1);
   lcd.print("A=     T=");

   pinMode(rele, OUTPUT);
};

void loop () {

  digitalWrite(LED, x);
 // lcd.print("volt=");
 lcd.setCursor(2,0);
  lcd.print(voltage);

 lcd.setCursor(10,0);
  lcd.print(capacity); 

lcd.setCursor(2,1);
  lcd.print(current);

min=time/60;
lcd.setCursor(9,1);
  lcd.print(min);

if (voltage>=2.5) digitalWrite(rele, HIGH);

if (voltage<=2.5) digitalWrite(rele, LOW);
};