voltmeter with arduino, associating a SD card

Hello!!
Im beginner and i don’t master the subject as well. Só, i kindly need your help with my project. My goal is gathet informations of voltage’s value with two solars plate (voltage greater than 5v)

I have one code on which execute this function but, i need to collect data during a full day and after put all the informations in a mamory Card. So , i would like to know how can i make a datalogger …this is my huge doubt.
I gonna use a aurduino uno SD card shield and the system to receive the current data.
I hope hearing from you soon. Kind regards.

float tensaoA2;
float tensaoA0;

float aRef=5;
float relacaoA0=11;
float relacaoA2=11;
#define AMOSTRAS 12

void setup() {
    Serial.begin(9600);
}

float lePorta(uint8_t portaAnalogica) {
  float total=0;  
  for (int i=0; i<AMOSTRAS; i++) {
    total += 1.0 * analogRead(portaAnalogica);
    delay(5);
  }
  return total / (float)AMOSTRAS;
}  

void mostraTensoes() {
  Serial.print("Tensao em A2: ");
  Serial.print(tensaoA2 * relacaoA2);
  Serial.print ("V / ");
  Serial.print("Tensao em A0: ");
  Serial.print(tensaoA0 * relacaoA0);
  Serial.println ("V");
}  

void loop() {
  tensaoA2 = (lePorta(A2) * aRef) / 1024.0;
  tensaoA0 = (lePorta(A0) * aRef) / 1024.0;
  mostraTensoes();
  delay(500);
}

current greater than 5v

Current is not measured in volts.

but, i need to collect data during a full day and after put all the informations in a mamory Card

That is not going to happen. During the day, you can collect data AND write it to the card. You are not going to save all the data and write it at the end of the day, unless you only take readings every 5 minutes.

i would like to know how can i make a datalogger ......this is my huge doubt!!!!

My huge doubt is why you need so many exclamation points. Why do you?

The SD class comes with examples. Have you looked at any of them?