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Battery Level Indicator Circuit using Arduino


 In this post, we are going to construct a battery level indicator using Arduino, where a series of 6 LEDs show the level of the battery. If you are interested in monitoring and maintenance of your 12V battery, this circuit might become handy.


By: Girish Radhakrishnan

All batteries have certain voltage limit to discharge, if it goes beyond the prescribed limit, the life span of the battery will reduce drastically.

Being electronics enthusiasts, we all might have a battery for testing our prototype circuits. Since we concentrate on the prototype during experiment, we care less on the battery.

The proposed circuit will show you how much energy left in the battery, this circuit may be connected to battery, while you prototyping your circuits. When this circuit indicates low battery, you may put the battery to charge. The circuit has 6 LEDs, one LED glow at a time to indicate the voltage level of the battery.

If your battery is full, the left most LED glows and you battery is dead or about to die, the right most LED glows.

The circuit:



Battery Level Indicator Circuit using Arduino


The circuit consists of Arduino which is the brain of the system, a potential divider which helps the Arduino to sample the input voltage. A pre-set resistor is used to calibrate the above setup. The series of 6 LEDs will indicate the battery level.

The relation between LED and battery level is given below:

LED1 – 100% to 80%

LED2 – 80% to 60%

LED3 – 60% to 40%

LED4 – 40% to 20%

LED5 – 20% to 5%

LED6 - <5% (charge your battery)

The Arduino measures a narrow range of voltage from 12.70V to 11.90V. A fully charged battery should have voltage above 12.70V after disconnecting from charger. A low battery voltage must not go below 11.90V for a 12V sealed lead-acid battery.

Author’s prototype:





Program:

//--------Program developed by R.Girish---------//

int analogInput = 0;
int f=2;
int e=3;
int d=4;
int c=5;
int b=6;
int a=7;
int s=13;
float vout = 0.0;
float vin = 0.0;
float R1 = 100000;
float R2 = 10000; 
int value = 0;
void setup()
{
Serial.begin(9600);
pinMode(analogInput,INPUT);
pinMode(s,OUTPUT);
pinMode(a,OUTPUT);
pinMode(b,OUTPUT);
pinMode(c,OUTPUT);
pinMode(d,OUTPUT);
pinMode(e,OUTPUT);
pinMode(f,OUTPUT);
digitalWrite(s,LOW);
digitalWrite(a,HIGH);
delay(500);
digitalWrite(b,HIGH);
delay(500);
digitalWrite(c,HIGH);
delay(500);
digitalWrite(d,HIGH);
delay(500);
digitalWrite(e,HIGH);
delay(500);
digitalWrite(f,HIGH);
delay(500);
digitalWrite(a,LOW);
digitalWrite(b,LOW);
digitalWrite(c,LOW);
digitalWrite(d,LOW);
digitalWrite(e,LOW);
digitalWrite(f,LOW);
}
void loop()
{
value = analogRead(analogInput);
vout = (value * 5.0) / 1024;
vin = vout / (R2/(R1+R2));
Serial.println("Input Voltage = ");
Serial.println(vin);
if(vin>12.46) {digitalWrite(a,HIGH);}
else { digitalWrite(a,LOW);}
if(vin<=12.46 && vin>12.28) {digitalWrite(b,HIGH);}
else { digitalWrite(b,LOW);}
if(vin<=12.28 && vin>12.12) {digitalWrite(c,HIGH);}
else { digitalWrite(c,LOW);}
if(vin<=12.12 && vin>11.98) {digitalWrite(d,HIGH);}
else { digitalWrite(d,LOW);}
if(vin<=11.98 && vin>11.90){digitalWrite(e,HIGH);}
else {digitalWrite(e,LOW);}
if(vin<=11.90) {digitalWrite(f,HIGH);}
else {digitalWrite(f,LOW);}
delay(2000);
}
//--------Program developed by R.Girish---------//

How to calibrate the circuit:

The calibration for this Arduino 6 LED battery level indicator circuit must be done carefully, if you did not calibrate correctly, the circuit will show incorrect voltage level of the battery.

When you turn on the circuit, it starts with LED test, where the LEDs glow up sequentially with some delay. This might help you to debug errors while arranging the LEDs.

1)    Set the voltage of your variable power supply to precisely to 12.50V.

2)    Open the serial monitor.

3)    Rotate the preset resistor clock wise or counter clock wise and bring the readings to 12.50V.

4)    Now, reduce the variable power supply to 12.00V, the readings on the serial monitor should show the same or very close to 12.00V

5)    Now, increase the voltage to 13.00V, the readings on serial monitor should also show the same or very close.

6)    At the same time when you increase or decrease the voltage, the each LED should turn on/off with different voltage levels.

Once the above steps are done successfully, your battery level indicator circuit will be ready to serve the intended purpose.


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24 comments:

  1. Hi Mr swagatam well I need to do my final year project. I need to do battery indicator using Bluetooth and wifi. My question is do I need to do a vdr to avoid a more volt supply to my arduino+LCD+bluetooth module. I hope you can help me

    ReplyDelete
    Replies
    1. Hi Fatin, you can use a 7805 IC voltage regulator for ensuring a safe 5V for the Arduino.

      Delete
  2. Hello;
    I have been searching for a circuit that can detect if lithium ion 4.2v rechargeable battery is at fault i mean consuming very less current like 10-100mA but not getting the proper charging current.With LED indication.

    ReplyDelete
    Replies
    1. Hello, the only way to detect this could be through a current sensing resistor and a voltage amplifier circuit which will indicate whether the cell is consuming around 1C current or not......LM3915 IC looks a candidate for making this system.

      Delete
  3. Can this be done using arduino with less parts i want to achieve the result.

    ReplyDelete
  4. I only need one LED to indicate so small opamp like lm393 can be use?.Please suggest a circuit.

    ReplyDelete
    Replies
    1. you can try the following concept, keep only one opamp instead of the shown 4

      http://www.homemade-circuits.com/2015/04/battery-current-indicator-circuit.html

      Delete
    2. ....connect the LED cathode to the input supply ground line.

      LED will ON for good battery and OFF for bad battery...for an opposite response connect the LED across opamp output and positive line.

      Delete
  5. can you provide a circuit for solar panel powered battery charging circuit that charges 12V 7Ah battery

    ReplyDelete
    Replies
    1. you can make the following circuit:

      http://www.homemade-circuits.com/2012/04/how-to-make-solar-battery-charger.html

      adjust the 10K to get exactly 14V for the battery, and use an input of 15V at 1 amp

      Delete
  6. Good evening....please sir how can i make the led to be constantly ON but Turn OFF when the battery is LOW

    ReplyDelete
  7. If a dead battery attached to this circuit but the battery is also attached to the charging circuit how can we get low battery indication?.As charger output is above 13v so the green LED ON instead of red LED.What to do?

    ReplyDelete
    Replies
    1. when a good battery is connected the supply voltage will instantly go down and settle down to the battery discharge level...but for a dead battery this might not happen and will indicate something's wrong with the battery.

      Delete
    2. Hi, Faizan

      Do not charge your battery along with this circuit, it won't indicate the correct battery level.

      Regards.

      Delete
  8. hello i have calibrated the circuit FOR LITHIUM ION battery charger i have connected the charger it shows 4.2v when no battery and when a 3.7v battery attached to it the serial monitor shows voltage more then 4.7v what to do?.Why it is not showing correct charging voltage or do i need to change the formula?

    ReplyDelete
    Replies
    1. Hello, Mr. Girish will hopefully see your question here and respond appropriately....please be patient.

      Delete
    2. Hi, Faizan,

      The circuit is NOT designed for Li-ion batteries, it is proposed for 12V SLA batteries.

      The code is written for 12V batteries and will not monitor 3.7V Li-ion batteries.

      Do not charge your batteries along with this circuit. It is designed to monitor the battery only on discharge.

      Please read the article properly, this will keep most of the misunderstanding about the project at bay .

      Regards

      Delete
  9. Its adding battery voltage as well

    ReplyDelete
  10. hy sir i make circuit same as above but the serial monitor shows 20+ reading without battery.
    and only secondary battery are use.

    ReplyDelete
    Replies
    1. Hi Unknown....LOL :)

      Please elaborate your issues and please comment you problem in a way that others can understand.

      Regards

      Delete
  11. Waiting for the reply anxiously.

    ReplyDelete
    Replies
    1. Please refer to your previous comment above, for the reply....

      Delete
  12. OK if i calibrate for Li battery but once charging circuit connects what will be the changes to be done to detect original voltage of battery under charge? instead it add up the battery voltage with the charging circuit voltage.

    ReplyDelete
  13. Hi faizan,

    You cannot calibrate the circuit for li-ion battery as the program is written for 12V battries only.

    That's why you are getting unusual voltage readings on serial monitor when you connect the charger.

    If you are looking for li-ion based projects this is not the right one.

    Regards

    ReplyDelete

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