int sensorPin = A0; 
int onboardLED = 13; 
int sensorValue = 0;
unsigned int batteryCapacity = 50000;
unsigned int batteryLevel = 0;
unsigned int ticks = 0; // represents time
unsigned int wait = 100; // represents wait time
double PercentFull;

void setup() {
  // put your setup code here, to run once:

     Serial.begin(9600);
     pinMode(onboardLED, OUTPUT);
}


void loop () {
  // put your main code here, to run repeatedly:

     sensorValue = analogRead(sensorPin);
     batteryLevel += sensorValue;
     ticks += wait;

     if(batteryLevel >= batteryCapacity) {
          Serial.print(ticks);
          Serial.print(" ms.    ");
          Serial.println("FULLY CHARGED");
          batteryLevel = batteryCapacity; // to prevent integer from continuing to increase.
          ticks = 0;
          delay(20000); // wait for 20 seconds.
     }
     else {
          PrintBatteryPercentage();
     }

     delay(wait);
}


void PrintBatteryPercentage() {

     Serial.print(ticks);
     Serial.print(" ms.    charge at  ");

    // convert the integers to decimal numbers, divide them and print to Serial Monitor
    PercentFull=100*((double)batteryLevel / (double)batteryCapacity);
    Serial.print(PercentFull);

    Serial.println("%"); // prints percentage sign and starts a new line.
}