Features:

Identify a fake Lithium-Ion/Lithium-Polymer/NiCd/NiMH battery

Adjustable constant current load (can also be modified by the user)

Capable of measuring the capacity of almost any kind of battery (below 5V)

Easy to solder, build, and use, even for beginners (all components are Dip)

An LCD user interface

Specifications:

Board Supply: 7V to 9V(Max)

Battery Input: 0-5V(max) – no reverse polarity

Constant Current Load: 37mA to 540mA(max) – 16 Steps – can be modified by the user

The true measurement of a battery’s capacity is essential for many scenarios. A capacity measurement device can solve the problem of spotting fake batteries as well. Nowadays fake Lithium and NiMH batteries are everywhere which don’t handle their advertised capacities. Sometimes it is difficult to distinguish between a real and a fake battery. This problem exists in the spare batteries market, such as cell phone batteries. Furthermore, in many scenarios, it is essential to determine the capacity of a second-hand battery (for instance a laptop battery). In this article, we will learn to build a battery capacity measurement circuit using the famous Arduino-Nano board. I’ve designed the PCB board for dip components. So even beginners can solder and use the device.

Schematic

PCB

Bill of Materials

Arduino Code

#include <LiquidCrystal.h>
#include <JC_Button.h>
 
const float Low_BAT_level = 3.2;
 
//Current steps with a 3R load (R7)
const int Current[] = {0, 37, 70, 103, 136, 169, 202, 235, 268, 301, 334, 367, 400, 440, 470, 500, 540};
 
const byte RS = 2, EN = 3, D4 = 4, D5 = 5, D6 = 6, D7 = 7;
const byte PWM_Pin = 10;
const byte Speaker = 12;
const int BAT_Pin = A0;
int PWM_Value = 0;
unsigned long Capacity = 0;
int ADC_Value = 0;
float BAT_Voltage = 0;
byte Hour = 0, Minute = 0, Second = 0;
bool calc = false, Done = false;
 
LiquidCrystal lcd(RS, EN, D4, D5, D6, D7);
 
Button UP_Button(16, 25, false, true);
Button Down_Button(15, 25, false, true);
 
void setup() {
 
  pinMode(PWM_Pin, OUTPUT);
  pinMode(Speaker, OUTPUT);
 
  analogWrite(PWM_Pin, PWM_Value);
 
  UP_Button.begin();
  Down_Button.begin();
 
  lcd.setCursor(0, 0);
  lcd.begin(16, 2);
  lcd.print("Battery Capacity");
  lcd.setCursor(0, 1);
  lcd.print("Measurement v1.0");
  delay(3000);
  lcd.clear();
  lcd.print("Load Adj:UP/Down");
  lcd.setCursor(0, 1);
  lcd.print("0");
 
}
 
void loop() {
  UP_Button.read();
  Down_Button.read();
 
  if (UP_Button.wasReleased() && PWM_Value < 80 && calc == false)
  {
    PWM_Value = PWM_Value + 5;
    analogWrite(PWM_Pin, PWM_Value);
    lcd.setCursor(0, 1);
    lcd.print("     ");
    lcd.setCursor(0, 1);
    lcd.print(String(Current[PWM_Value / 5]) + "mA");
  }
 
  if (Down_Button.wasReleased() && PWM_Value > 1 && calc == false)
  {
    PWM_Value = PWM_Value - 5;
    analogWrite(PWM_Pin, PWM_Value);
    lcd.setCursor(0, 1);
    lcd.print("     ");
    lcd.setCursor(0, 1);
    lcd.print(String(Current[PWM_Value / 5]) + "mA");
  }
  if (UP_Button.pressedFor(1000) && calc == false)
  {
    digitalWrite(Speaker, HIGH);
    delay(100);
    digitalWrite(Speaker, LOW);
    lcd.clear();
    timerInterrupt();
  }
 
}
 
void timerInterrupt() {
  calc = true;
  while (Done == false) {
    Second ++;
    if (Second == 60) {
      Second = 0;
      Minute ++;
      lcd.clear();
    }
    if (Minute == 60) {
      Minute = 0;
      Hour ++;
    }
    lcd.setCursor(0, 0);
    lcd.print(String(Hour) + ":" + String(Minute) + ":" + String(Second));
    lcd.setCursor(9, 0);
    ADC_Value = analogRead(BAT_Pin);
    BAT_Voltage = ADC_Value * (5.0 / 1024);
    lcd.print("V:" + String(BAT_Voltage));
    lcd.setCursor(0, 1);
    lcd.print("BAT-C: Wait!...");
 
    if (BAT_Voltage < Low_BAT_level)
    {
      lcd.setCursor(0, 1);
      lcd.print("                ");
      lcd.setCursor(0, 1);
      Capacity =  (Hour * 3600) + (Minute * 60) + Second;
      Capacity = (Capacity * Current[PWM_Value / 5]) / 3600;
      lcd.print("BAT-C:" + String(Capacity) + "mAh");
      Done = true;
      PWM_Value = 0;
      analogWrite(PWM_Pin, PWM_Value);
      digitalWrite(Speaker, HIGH);
      delay(100);
      digitalWrite(Speaker, LOW);
      delay(100);
      digitalWrite(Speaker, HIGH);
      delay(100);
      digitalWrite(Speaker, LOW);
    }
 
    delay(1000);
  }
}