BMS_Ard_Code.ino

//Libraries required for temperature sensor are added.
#include <OneWire.h>
#include <DallasTemperature.h>

//Temperature sensor pin and variable defined.
#define ONE_WIRE_BUS 4
OneWire oneWire(ONE_WIRE_BUS);
DallasTemperature sensors(&oneWire);

//Digital pins controlling relays are named.
int R1 = 6;
int R2 = 7;
int R3 = 8;
int R4 = 9;
int R5 = 10;
int R6 = 11;
int HB_to_Cap = 12;
int Cap_to_LB = 13;
int Role_pin = 5;

//Global variables of SoC calculation are defined.
int lastTime1 = 0;
int nowTime1 = 0;
long T_diff = 0;
double total_Ah = 0;
double total_Ah_discharge = 0;
double total_Ah_charge = 0;
double guncel_Ah = 0;
double Cap_Ah = 3.3;

//SoC correcting flag
int soc_corr_flag = 0;

//int kontak_sure = 500; //c-balance ile batt.'larin bagli kalma sureleri
//int min_dengeleme_tekrari = 100;

//Resistor values for voltage calculation are defined.
//Real values of resistors are used for precision.
float r3 = 9.98;
float r4 = 98.6;
float r22 = 56.0;
float r21 = 46.5;
float r24 = 76.4;
float r23 = 32.6;

//Voltage values are defined.
float V_volt_1 = 0;
float V_volt_2 = 0;
float V_volt_3 = 0;

bool ISIK = 0;

double I_amp1 = 0;
double SoC;
float T = 0;

//Global values for balancing are defined.
int max_cell = 0;
int min_cell = 0;

float max_volt = 0;
float min_volt = 0;

int denge_cycle_no = 10;

bool balance_ok = 1;

//Void setup is run once at the beginning.
void setup() {
  //Baudrate is given.
  Serial.begin(112500);
  
  //All digital pins are set whether they are inputs or outputs.
  pinMode(2, INPUT_PULLUP);
  pinMode(3, INPUT_PULLUP);
  pinMode(4, INPUT);
  pinMode(5, OUTPUT);
  pinMode(6, OUTPUT);
  pinMode(7, OUTPUT);
  pinMode(8, OUTPUT);
  pinMode(9, OUTPUT);
  pinMode(10, OUTPUT);
  pinMode(11, OUTPUT);
  pinMode(12, OUTPUT);
  pinMode(13, OUTPUT);

  //Initial values if the relays are set to LOW except emergency relay to prevent any short circuits between cells.
  digitalWrite(R1, LOW);
  digitalWrite(R2, LOW);
  digitalWrite(R3, LOW);
  digitalWrite(R4, LOW);
  digitalWrite(R5, LOW);
  digitalWrite(R6, LOW);
  digitalWrite(HB_to_Cap, LOW);
  digitalWrite(Cap_to_LB, LOW);
  digitalWrite(Role_pin, HIGH);
}

//A function to disconnect batteries.
void All_BATT_Disconnect (){
  digitalWrite(R1, LOW);
  digitalWrite(R2, LOW);
  digitalWrite(R3, LOW);
  delay(200);
  digitalWrite(R4, LOW);
  digitalWrite(R5, LOW);
  digitalWrite(R6, LOW);
  delay(200);
}

//A function to choose B1 and B2.
void BATT1_to_BATT2_contact (){
  All_BATT_Disconnect();
  digitalWrite(R4, HIGH);
  digitalWrite(R5, LOW);
  digitalWrite(R6, LOW);
  delay(200);
  digitalWrite(R1, HIGH);
  digitalWrite(R2, HIGH);
  digitalWrite(R3, LOW);
  delay(200);
}

//A function to choose B1 and B3.
void BATT1_to_BATT3_contact (){
  All_BATT_Disconnect();
  digitalWrite(R4, HIGH);
  digitalWrite(R5, LOW);
  digitalWrite(R6, LOW);
  delay(200);
  digitalWrite(R1, HIGH);
  digitalWrite(R2, LOW);
  digitalWrite(R3, HIGH);
  delay(200);
}

//A function to choose B2 and B3.
void BATT2_to_BATT3_contact (){
  All_BATT_Disconnect();
  digitalWrite(R4, LOW);
  digitalWrite(R5, HIGH);
  digitalWrite(R6, LOW);
  delay(200);
  digitalWrite(R1, LOW);
  digitalWrite(R2, HIGH);
  digitalWrite(R3, HIGH);
  delay(200);
}  

//A function to balance two chosen cells.
void Dengele (int Count){
  Serial.print(" BALANCING= ");
  Serial.print(max_cell);
  Serial.print(" - ");
  Serial.print(min_cell);
  Serial.print("| ");
  int i = 0;
  while (i < Count)
  {
    digitalWrite(HB_to_Cap, HIGH);
    //AQZ205 Turn on time 5.8 ms
    delay(6);
    //Full Battery => Capacitor
    delay(2);
    digitalWrite(HB_to_Cap, LOW);
    //AQZ205 Turn off time 0.2 ms
    delay(1);
    digitalWrite(Cap_to_LB, HIGH);
    //AQZ205 Turn on time 5.8 ms
    delay(6);
    //Capacitor => Low Battery
    delay(2);
    digitalWrite(Cap_to_LB, LOW);
    //AQZ205 Turn off time 0.2 ms
    delay(1);

    i++;
  }
    //Solid state relays are left LOW to prevent short circuit.
    digitalWrite(Cap_to_LB, LOW);
    digitalWrite(HB_to_Cap, LOW);
}

//A function to read and print voltage values of 3 Li-ions cells.
void BATT_V_oku() {
  //Local raw analog sensor values are defined.
  int V_raw_sensor_value_1 = 0;
  int V_raw_sensor_value_2 = 0;
  int V_raw_sensor_value_3 = 0;

  float V_temp_1 = 0;
  float V_temp_2 = 0;
  float V_temp_3 = 0;

  //Analog values are read.
  V_raw_sensor_value_1 = analogRead(A3);
  V_raw_sensor_value_2 = analogRead(A4);
  V_raw_sensor_value_3 = analogRead(A5);

  //Voltage values are calculated considering each resistance value.
  V_temp_1 = (V_raw_sensor_value_1 * 5.0) / 1023.0; // FORMULA USED TO CONVERT THE VOLTAGE
  V_volt_1 = V_temp_1 / (r4/(r3+r4));

  V_temp_2 = (V_raw_sensor_value_2 * 5.0) / 1023.0; // FORMULA USED TO CONVERT THE VOLTAGE
  V_volt_2 = V_temp_2 / (r21/(r22+r21));

  V_temp_3 = (V_raw_sensor_value_3 * 5.0) / 1023.0; // FORMULA USED TO CONVERT THE VOLTAGE
  V_volt_3 = V_temp_3 / (r23/(r24+r23));

  V_volt_2 = V_volt_2 - V_volt_1;
  V_volt_3 = V_volt_3 - V_volt_2 - V_volt_1;

  //Voltage values are printed.
  Serial.print(" V1= ");
  Serial.print(V_volt_1);
  Serial.print("| ");

  Serial.print(" V2= ");
  Serial.print(V_volt_2);
  Serial.print("| ");
  
  Serial.print(" V3= ");
  Serial.print(V_volt_3);
  Serial.print("| ");

}

//A function to read and print current value.
void BATT_I_oku() {
  //Local raw analog sensor value is defined.
  int I_raw_sensor_value_1 = 0;
  //Analog value is read.
  I_raw_sensor_value_1 = analogRead(A0);
  //Current value in A is calculated
  //considering the output of MAX471.
  I_amp1 = I_raw_sensor_value_1 * (5.0 / 1023.0);

  //Current values are digitally filtered.
  if(I_amp1 < 0.09){
    I_amp1 = 0;
  }

//==========================================================================================

  //Millisecond value is taken to be used in SoC calculation.
  nowTime1 = millis();
  //Considering the differentiation of the main loop,
  //time difference is taken into account.
  T_diff = nowTime1 - lastTime1;
  lastTime1 = nowTime1;

  //Millisecond is converted into hours.
  double T_diff_sec = (float)T_diff / 1000;
  double T_diff_min = T_diff_sec / 60;
  double T_diff_h = T_diff_min / 60;

  //Ah spent in each measurement is calculated.
  double Ah = T_diff_h * I_amp1;

  //Detection of whether charging or dishcarging is made using 2 digital inputs.
  int C = digitalRead(2);
  int D = digitalRead(3);

  if(D == 1 && C == 0){           //Ah of discharging substracted from SoC
    soc_corr_flag = 1;
    total_Ah_discharge += Ah;
    SoC = (Cap_Ah - total_Ah_discharge) / Cap_Ah * 100;
    guncel_Ah = Cap_Ah - total_Ah_discharge;
  } else if(C == 1 && D == 0){    //Ah of charging added to SoC
    soc_corr_flag = 1;
    total_Ah_charge += Ah;
    SoC = (guncel_Ah + total_Ah_charge) / Cap_Ah * 100;
  } else {                        //Idle state - SoC correction flag is changed
    if(soc_corr_flag == 1){       //just to prevent SoC from starting as 0%
      soc_corr_flag = 1;
    }
  }
  //total_Ah += Ah;
  if(soc_corr_flag == 0){
    SoC = 100;
  }
  
  if(SoC > 100){
    SoC = 100;
  }
  
//==========================================================================================

  //Printing current value in Amperes.
  Serial.print(" I= ");
  Serial.print(I_amp1);
  Serial.print("| ");

  //Printing SoC value in percentage.
  Serial.print(" SoC = ");
  Serial.print(" %");
  Serial.print(SoC, 6);
  Serial.print("| ");

}

//A function to read and print temperature value.
void BATT_T_oku() {
  //Sensor value is read.
  sensors.requestTemperatures();
  T = sensors.getTempCByIndex(0);
  
  //Sensor value is printed.
  Serial.print(" T= ");
  Serial.print(T);
  Serial.println("| ");
}

//A funtion to find max and min voltage cells.
void min_max_cell_bul(){
  max_cell = 0;
  min_cell = 0;

  max_cell = 1;
  min_cell = 1;

  max_volt = V_volt_1;
  min_volt = V_volt_1;

  if(V_volt_2 < min_volt){
    min_volt = V_volt_2;
    min_cell = 2;
  }

  if(V_volt_3 < min_volt){
    min_volt = V_volt_3;
    min_cell = 3;
  }

  if(V_volt_2 > max_volt){
    max_volt = V_volt_2;
    max_cell = 2;
  }

  if(V_volt_3 > max_volt){
    max_volt = V_volt_3;
    max_cell = 3;
  }
}

//A function to change balance_ok flag.
//balance_ok flag exists to prevent
//balancing in not ordinary conditions.
void balance_check(){
  if(V_volt_1 < 3 || V_volt_1 > 4.5 || V_volt_2 < 3 || V_volt_2 > 4.5 || V_volt_3 < 3 || V_volt_3 > 4.5){
    balance_ok = 0;
  }
}

//-MAIN-LOOP-
void loop() {
  //Flag is refreshed at the beginning of each loop.
  balance_ok = 1;
  //Voltage values are read.
  BATT_V_oku();
  //Flag is updated.
  balance_check();
  //Current value is read.
  BATT_I_oku();
  //Temperature value is read.
  BATT_T_oku();
  //Max and min cells are found.
  min_max_cell_bul();

  //If balance_ok flag is one and voltage difference is larger than 0.2,
  //balancing is done between chosen max and min cells.
  //Because of the fact that balancing
  if(max_volt - min_volt > 0.2 && balance_ok == 1){
    switch (max_cell) {
      case 1:
          switch (min_cell)
          {
          case 2:
          BATT1_to_BATT2_contact();
          Dengele(denge_cycle_no);
          break;

          case 3:
          BATT1_to_BATT3_contact();
          Dengele(denge_cycle_no);
          break;

          default:
          break;
          }
      break;

      case 2:
          switch (min_cell)
          {
          case 1:
          BATT1_to_BATT2_contact();
          Dengele(denge_cycle_no);
          break;

          case 3:
          BATT2_to_BATT3_contact();
          Dengele(denge_cycle_no);
          break;

          default:
          break;
          }
      break;

      case 3:
          switch (min_cell)
          {
          case 1:
          BATT1_to_BATT3_contact();
          Dengele(denge_cycle_no);
          break;

          case 2:
          BATT2_to_BATT3_contact();
          Dengele(denge_cycle_no);
          break;

          default:
          break;
          }
      break;

      default:
      break;
    }
  }

  // If V, I and T values are at extreme amounts
  // such that they would cause an emergency
  // Safety relay is set to open and takes out
  // from the rest of the ciruit.
  if(V_volt_1 > 4.5 || V_volt_2 > 4.5 || V_volt_3 > 4.5 || I_amp1 > 3 || V_volt_1 < 2 || V_volt_2 < 2 || V_volt_3 < 2 || T > 50){
    digitalWrite(Role_pin, LOW);
  }
  //A string named Interface which consists of measured and processed variables,
  //is formed to send values to the personal computer for interface.
  Interface = "|V1=" + String(V_volt_1,6) + "|V2=" + String(V_volt_2,6) + "|V3=" + String(V_volt_3,6) + "|I=" + String(I_amp1,6) + "|SoC" String(I_amp1,6) +  "|T=" + String(T,6) );
  Serial.println(Interface);
  
}