Blutooth Based Auto Cutoff Charger

void setup()
{
Serial.begin(9600); // buart rate
pinMode(13,OUTPUT); // RELAY MODULE
digitalWrite(13,LOW); // relay module high
}
void loop()
{
    if(Serial.available()>0)
    {
      char data= Serial.read();
      Serial.println(data);
       if(data=='1')
       {
         digitalWrite(13,LOW); // RELAY ON
         Serial.println("RELAY");
       }
       if(data=='0')
       {
       digitalWrite(13,HIGH); // RELAY OFF
       Serial.println("RELAY");
       }
    }
}