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Battery Level Indicator Circuit using Arduino

Last Updated on by 42 Comments

In this post, we are going to construct an Arduino based  battery level indicator, 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

Why Battery Level Monitoring is Crucial

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 battery charger 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.

How it Works

 



LED battery level indicator using Arduino code

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.

Calibrating LED Indicators

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:

Arduino Battery level indicator prototype

Program Code:

//--------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 Setup 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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Forum Discussion - Ask a Question

  3. HI, In this the voltage level is indicated in the form of a LED. If it is possible to get the voltage level in the digital format

    Reply

  5. what if i want to indicate the battery level in percentage form on an lcd display instead of using LEDS, what can i do?? please advice

    Reply

  6. Thank you sir.
    Actually I want to design a controller circuit for stand alone pv system to energize the 12V DC bus. This controller must have the MPPT (with P & O algorithm). normally systems disconnected at the overcharging and over discharging the 12V battery.
    I want to design a controller to disconnect MPPT at the battery charging is greater than the 95% ,then it track the voltage without MPPT until 100% charging. if the charging level less than the 95% then it connect to the MPPT again. can it do this by using arduino. ?
    {i want to prevent the problem of cut off the MPPT at the No-load and fix this disconnection & re-connection in smoothly}

    Reply

    • Dinuasha, if your requirement is to keep the charging thresholds within the margin of 100% and 95%, then I think it could be done with a simple opamp circuit, using Arduino will be an overkill for such a a simple operation.

      Reply

  7. Dear sir,
    Is it only use the battery terminal voltage as input? can i used this for stand alone PV system (12V battery monitoring)?.Because I want to disconnect the battery from the load or pv array at the required charging levels.

    Reply

  8. Hi,
    I need to do battery level circuit for my intern project. The will be 5v at the input and there will be five leds. For example if there is 1v just one of the leds will light then for 2v first two of themcan you help me about this?

    Reply

    • Hi, Gizem

      Are you sure about your design, because a 5V (4.5v etc) battery should not be allowed to fall to 1 Volt and most of the circuit will only work above 3V in general.

      I will design a circuit for you, if you want me to proceed with your requirements.

      Regards

      Reply

  9. 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

    Reply

  10. 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.

    Reply

  14. 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?

    Reply

    • 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

      Reply

  15. 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?

    Reply

    • 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.

      Reply

    • you can make the following circuit:

      https://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

      Reply

    • you can try the following concept, keep only one opamp instead of the shown 4

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

      Reply

    • ….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.

      Reply

  20. 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.

    Reply

    • 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.

      Reply

  21. 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

    Reply

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