/* Be sure you have a voltage divider 4:1 to measure the battery voltages. Battery--[4k]----[1k]--GND
 *                                                                                        |
 *                                                                                    [Arduino]

Sens:
Battery 1 is (thru voltage divider) on Pin A0
Battery 2 is (thru voltage divider) on Pin A1

Relais for Batteries:
On Digital 2: Relais to connect Battery 1 to load
On Digital 3: Relais to connect Battery 1 to charger
On Digital 4: Relais to connect Battery 2 to load
On Digital 5: Relais to connect Battery 3 to charger
*/



/* Constants and Inits */
unsigned int rereads = 0;           // we want to make a multiple-read on the battery to be sure it is not only a spike...
float voltagesum = 0;               // The sum of 100x reading of battery in float
int b1l = 2;                        // Definitions for pins
int b1c = 3;                        // Definitions for pins
int b2l = 4;                        // Definitions for pins
int b2c = 5;                        // Definitions for pins


/* Setup */
float batteryempty = 11.8;          // Empty battery according to https://www.tobesure.com/2018/11/06/what-is-the-voltage-of-a-car-battery-harrisburg-pa/

void setup() {
  // put your setup code here, to run once:
  pinMode(A0, INPUT);     // sets the analog A0 to input --> Sens for battery 1
  pinMode(A1, INPUT);     // sets the analog A1 to input --> Sens for battery 2
  pinMode(b1l, OUTPUT);     // sets the digital 2 to output --> Control of relais for battery 1, Dischargepath
  pinMode(b1c, OUTPUT);     // sets the digital 3 to output --> Control of relais for battery 2, Dischargepath
  pinMode(b2l, OUTPUT);     // sets the digital 4 to output --> Control of relais for battery 1, Chargepath
  pinMode(b2c, OUTPUT);     // sets the digital 5 to output --> Control of relais for battery 2, Chargepath

  digitalWrite(b2l, LOW);   // Battery 1 OFF for charge
  digitalWrite(b1l, HIGH);  // Battery 1 ON for discharge
  digitalWrite(b2c, HIGH);  // Battery 2 ON for charge
  digitalWrite(b1c, LOW);   // Battery 2 OFF for discharge
}



void loop() {
  float bat1voltage = 5 * analogRead(A0);
  if (bat1voltage <= batteryempty) {  // Battery 1 triggered a low indicator!
    for (int i = 0; i <= 100; i++) { // Measure over 2sec every < 20ms
      voltagesum = voltagesum + analogRead(A0);
      delay(17); // Allow 1ms for analog read... have it a bit faster than 1per20ms to avoid powerline-frequencies
    }
    bat1voltage = 1.0 * voltagesum / 100; // * 1.0 to force float
    voltagesum = 0;
    // Now we have an average of the battery-voltage over around 2secs.
    if (bat1voltage <= batteryempty) {
      digitalWrite(b1c, HIGH);  // Battery 1 ON for charge
      digitalWrite(b1l, LOW);   // Battery 1 OFF for load/discharge
      digitalWrite(b2c, LOW);   // Battery 2 OFF for charge
      digitalWrite(b2l, HIGH);  // Battery 2 ON for load/discharge
      continue;               // Skips rest of mainloop and starts a new iteration
    }
  }

  float bat2voltage = 5 * analogRead(A1);
  if (bat2voltage <= batteryempty) {  // Battery 2 triggered a low indicator!
    for (int i = 0; i <= 100; i++) {  // Measure over 2sec every < 20ms
      voltagesum = voltagesum + analogRead(A0);
      delay(17); // Allow 1ms for analog read... have it a bit faster than 1per20ms to avoid powerline-frequencies
    }
    bat2voltage = 1.0 * voltagesum / 100; // * 1.0 to force float
    voltagesum = 0;
    // Now we have an average of the battery-voltage over around 2secs.
    if (bat2voltage <= batteryempty) {
      digitalWrite(b1c, LOW);   // Battery 1 OFF for charge
      digitalWrite(b1l, HIGH);  // Battery 1 ON for load/discharge
      digitalWrite(b2c, HIGH);  // Battery 2 ON for charge
      digitalWrite(b2l, LOW);   // Battery 2 OFF for load/discharge
    }
  }
}