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Arduino Battery Level Indicator Circuit

Arduino Battery Level Indicator Circuit

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: Arduino Guru

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()
void loop()
value = analogRead(analogInput);
vout = (value * 5.0) / 1024;
vin = vout / (R2/(R1+R2));
Serial.println("Input Voltage = ");
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);}
//--------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.


About the Author

I am an electronic engineer (dipIETE ), hobbyist, inventor, schematic/PCB designer, manufacturer. I am also the founder of the website: https://www.homemade-circuits.com/, where I love sharing my innovative circuit ideas and tutorials. If you have any circuit related query, you may interact through comments, I'll be most happy to help!

62 thoughts on “Arduino Battery Level Indicator Circuit”

  1. sir i intend to construct a battery percentage monitor for a led lamp. how possible is this and how can i go about it?

  2. Hi sir! dear sir i want to add hysteresis feature to this battery monitor so that battery upper threshold level (cut off point) = 14.4v, lower threshold level(charging start point) = 12v by adding a relay to a battery charger with the same led display using arduino. my problem is what to do with the code to add hysteresis feature so that when the battery full it my not start charging until it reach back to 12v?

    • Hi Sheraz, actually code modification may not be required, it could be easily done through an external opamp circuit, if possible I’ll try to update it soon….

  3. Hy mr.Swagatam
    i have home work to do project about controller baterry/automatic charging using Arduino Uno,MOSFET/Transistor and Voltage sensor…
    i’m still confuged in arduino program code during charger and dischsarge….
    may you help me…

    • Hi Melchior, the above circuit can be easily converted into an auto cut-off system by integrating a mosfet stage with the appropriately selected outputs from the Arduino.

      Let me know if you want me to do this modification in the above circuit??

  4. Hi sir! dear sir how can we detect the presence of a 12v battery & the charger say 12v-10amp smps charging that 12v battery using arduino at the same time? my problem is if arduino adc channel measure the voltage using led display between battery terminals while connected to battery then the circuit is correct but if we disconnect battery from the charger how the arduino will detect the absence of charger terminal at battery terminal? i mean how arduino will detect presence or absence of charger at battery terminals?

    • Hi Sheraz, When you connect an external voltage to a battery, the external voltage will sink and merge with the battery voltage to become a common voltage.

      Suppose your battery is at 11V, and if you connect a 12V to it, then this 12V will instantly drop to 11V across the battery terminals, and then the battery will begin absorbing this voltage and charge until its terminal voltage reaches 12V. Once this happens, the charging will stop and both the sources will continue to be at this level as long as they are connected together.

      Similarly, if you connect 14V, the final voltage will settle at 14V while the charger is connected.

      So the only way to distinguish whether a charger is connected or not is through a current sensor stage, because the battery will begin drawing current from the charger while it’s being charged and this could be used for monitoring the presence or absence of the charger input.

      • sir i ‘m going to implement 10amp-12v smps design with an additional auto cutoff circuit using atmega8 and by placing 4 leds for 25%, 50%, 75% & finally 100% i will display this percent using atmega8 adc channel, like the circuit you presented in this article, i think if we power the atmega8 circuit by getting 5v from charger terminal by using some regulator then we will have to still use current sense circuit to know that whether battery is charging or not. without current sense circuit the display with also show that battery is 100% charge because the controller may sense the 12v-volt at the charger terminal if battery is disconnected. you are right sir by using current sense circuit this problem can be corrected.

  5. Hello Sir, may I ask a favor again to help me design a circuit for me to control my three-phase motor using remote control thank you and God bless,..

  6. hello Sir, kindly suggest a circuit of your own design which useful to control 3 phase motor by not just merely using start-stop that can easily be worn out due to sparks and may I ask further if can I make it wireless thanks…

  7. 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

  8. 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

  9. 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}

    • 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.

  10. 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.

    • Dear Dinusha,

      Yes you can use it separately for monitoring battery only, the Arduino can be powered from the battery under monitor.

  11. 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?

    • 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.


  12. 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.


  13. 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.

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

    • Hi Unknown….LOL 🙂

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


  15. 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?

    • 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 .


  16. 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?

  17. 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.

    • 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.

  18. 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

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