18650 Battery capacity checker -

Some of you know, I really like lithium ion batteries

*shocked*

Shut it! This is a short post, I don’t need you hamming up the works.

Just wait till I show up in your videos….

You wouldn’t….

Hello….

Oh hell…..

Ok, lets not worry about that now.

I picked up a pretty sweet haul of batteries this week.

22lbs. I counted 107 2cell packs. 214 cells to check out. This is great, but I have a single opus charger that can do 4 cells at a time.

So 214 cells will take some time to process. I have done that game. So I wanted to do more cells. There are examples online of doing this with arduino’s and what not and since I am big fan of arduino’s anyways I decided to give that a shot. I built it out initially with an arduino uno. Using the awesome guidance of Adam Welch. If you don’t know who Adam is, you gotta check out his work.

Website: http://adamwelch.co.uk/
Youtube: https://www.youtube.com/channel/UCm5sG3-BXQZfVy3st2T_XKg

His work I used for this is here.

I modified the code a little as I didn’t have that screen. I have a 20×4 screen. I also updated mine to calculate the voltage reference from the internal 1.1v reference.

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*/
* Battery Capacity Checker
* Uses Nokia 5110 Display
* Uses 1 Ohm power resister as shunt - Load can be any suitable resister or lamp
*
* YouTube Video: https://www.youtube.com/embed/qtws6VSIoYk
*
* http://AdamWelch.Uk
*
* Required Library - LCD5110_Graph.h - http://www.rinkydinkelectronics.com/library.php?id=47
*/

#include &lt;LiquidCrystal_I2C.h&gt;
#define gatePin 2
#define highPin A0
#define lowPin A1

boolean finished = false;
int interval = 5000; //Interval (ms) between measurements

float mAh = 0.0;
float shuntRes = 1.0; // In Ohms - Shunt resistor resistance

float current = 0.0;
float battVolt = 0.0;
float shuntVolt = 0.0;
float battLow = 2.9;

LiquidCrystal_I2C lcd(0x27,20,4);
unsigned long previousMillis = 0;
unsigned long millisPassed = 0;

void setup() {
  analogReference(INTERNAL);
  Serial.begin(115200);
  lcd.init(); //initialize the lcd
  lcd.backlight(); //open the backlight
  Serial.println("Battery Capacity Checker v1.1");
  Serial.println("battVolt current mAh");

  pinMode(gatePin, OUTPUT);
  digitalWrite(gatePin, LOW);

  lcd.setContrast(68);

  lcd.clear();

  lcd.print("Battery");
  lcd.print("Check");
  lcd.print("Please Wait");
  lcd.print("AdamWelch.Uk");

  delay(2000);
  lcd.clear();
}

void loop() {
  voltRef = readVcc() / 1024.0;
  Serial.print("Volt Ref: ");
  Serial.println(voltRef);
  battVolt = analogRead(highPin) * voltRef / 1024.0;
  Serial.print("Batt Vol: ");
  Serial.println(battVolt);

  shuntVolt = analogRead(lowPin) * voltRef / 1024.0;
  Serial.print("Shunt Val: ");
  Serial.println(shuntVolt);
  Serial.println();
  Serial.println();
  /*
  Serial.print(battVolt);
  Serial.print("\t");
  Serial.print(current);
  Serial.print("\t");
  Serial.println(mAh);
  */
  if(battVolt &gt;= battLow && finished == false)
  {
    digitalWrite(gatePin, HIGH);
    millisPassed = millis() - previousMillis;
    current = (battVolt - shuntVolt) / shuntRes;
    mAh = mAh + (current * 1000.0) * (millisPassed / 3600000.0);
    previousMillis = millis();

    lcd.setCursor(0,0);
    lcd.print("Discharge ");
    lcd.setCursor(0,1);
    lcd.print("Volt:");
    lcd.print(battVolt);
    lcd.print("v ");
    lcd.setCursor(0,2);
    lcd.print("Current:");
    lcd.print(current);
    lcd.print("a ");
    lcd.setCursor(0,3);
    lcd.print(mAh);
    lcd.print("mAh ");
    lcd.print("Running ");



  }
  if(battVolt &lt; battLow)
  {
    digitalWrite(gatePin, LOW);

    finished = true;



    lcd.clear();
    lcd.print("Discharge");
    lcd.print("Voltage:");
    lcd.print(battVolt);
    lcd.print("v");

    lcd.print(mAh);
    lcd.print("mAh");
    lcd.setCursor(0,1);
    lcd.print("Complete");


  }
  delay(interval);
}

long readVcc() {
  long result;
  // Read 1.1V reference against AVcc
  ADMUX = _BV(REFS0) | _BV(MUX3) | _BV(MUX2) | _BV(MUX1);
  delay(2); // Wait for Vref to settle
  ADCSRA |= _BV(ADSC); // Convert
  while (bit_is_set(ADCSRA,ADSC));
  result = ADCL;
  result |= ADCH&lt;&lt;8;
  result = 1126400L / result; // Back-calculate AVcc in mV
  return result;
}

Next step is to add a “charging” function with a tp4056 so I can charge then discharge.

Amazon – 5 for 6.95

Ebay – 10 for 4.95

Aliexpress – 10 < 2 bucks.

Once that is working I should be able to add a couple more modules. I have been really looking towards doing something with Brett Wattys 8 module charger. That things is INTENSE!!!