int voltagepin = A1;
int powerswitch = 1;
int mains = 0;
int shutmedown = 4;

void setup() {
  // put your setup code here, to run once:
  //Set Pin In/Out
  pinMode(powerswitch, OUTPUT);
  pinMode(shutmedown, OUTPUT);
  pinMode(voltagepin, INPUT);
  pinMode(mains, INPUT);
  delay(5000);
  bootup();

}

void loop() {
  // put your main code here, to run repeatedly:
  if (!digitalRead(mains) && digitalRead(powerswitch) && analogRead(voltagepin)<402 ){
    digitalWrite(shutmedown,HIGH);
    delay(25000);
    digitalWrite(powerswitch,LOW);
    digitalWrite(shutmedown,LOW);
    delay(5000);
  }

  if(!digitalRead(powerswitch) && analogRead(voltagepin)>400 && digitalRead(mains)){
    digitalWrite(powerswitch,HIGH);
  }

  delay(10);

}

void bootup()
{
  bool flag = false;

  while( flag == false ) //while charging lock in loop till voltage is above ref and mains is on

    {
      flag = digitalRead(mains) && analogRead(voltagepin)>400;
      //Karl Agius was here ^^^^^^^^^
      delay(500);//little wait
    }
  //Once Flag true Power On
  digitalWrite(powerswitch,HIGH);
  delay(10000); //bootup time
}