This module is based on principle of resistive voltage divider design,
can make the red terminal connector input voltage to 5 times smaller.Arduino analog input voltages up to 5 v,
the voltage detection module input voltage not greater than 5Vx5=25V
(if using 3.3V systems, input voltage not greater than 3.3Vx5=16.5V).
Arduino AVR chips have 10-bit AD, so this module simulates a resolution of 0.00489V (5V/1023),
so the minimum voltage of input voltage detection module is 0.00489Vx5=0.02445V.
Voltage input range : DC0-25 V
Voltage detection range : DC0.02445 V-25 V
Voltage analog resolution : 0.00489 V
Output Interface : "+ " connected 5/3.3V, "-" connected GND, "s" connected Arduino AD pins
DC input interface : red terminal positive with VCC, negative with GND
By 3P connector, connect this module with the expansion of board Arduino,
not only makes it easier for you to detect voltage battery,
can also use the IICLCD1602 LCD to display voltage.

Reference Code：

#include <Wire.h>

int val11;
int val2;

void setup()
{
pinMode(LED1,OUTPUT);
Serial.begin(9600);
Serial.println("Emartee.Com");
Serial.println("Voltage: ");
Serial.print("V");
}
void loop()
{
float temp;
val11=analogRead(1);
temp=val11/4.092;
val11=(int)temp;//
val2=((val110)/10);
Serial.println(val2);
delay(1000);
}