Arduino Voltmeter (Cars Battery Measurement System)




About: Hey I´m Dominik ! I´m an electronics technician in an apprenticeship. I`m 19 years old and working with arduino and microcontrollers since I started my apprenticeship. Feel free to ask me anything :D

Have you ever wanted a selfmade, opensource Voltmeter for your car ?

Please do not measure higher voltage than 12V!

With some low-cost electronic parts, you will build this in a few minutes!

Parts of this project: -> Arduino Uno or Duemilanove (available here: )

-> LC Display (16x2) (available here: )

-> Breadboard (available here: )

-> Some jumpers ( available here: )

-> A potentiometer 10k Ω ( available here: )

-> 1x 10 kΩ resistor, 1x 14 kΩ resistor, 1x Z-Diode (5,1V)

-> Arduino IDE ( available here: )


If you like this project, please vote for it! Just click on the orange vote button in the upper right hand corner and click vote! I would really appreciate it!


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Step 1: Creating the Electrical Circuit:

First of all, we have to search for the LC Display - Datasheet on the Internet. In this case, I used this Display here:

---> Open now the Arduino IDE, click on "data", click on "samples" , click on "Liquid Crystal" and load the "Hello World" -Sketch.

Now you are able to create your electrical circuit...

After all you can prove your electrical circuit, load the "Hello World" - Sketch, the LCD should work now.

Step 2: Modify the Existing Circuit:

Ok.. Lets go to an interesting part:

For example, if you would like to measure the voltage of your cars battery, take your arduino voltmeter:

Princip of the Circuit:

-> The measurecircuit exists of a simple voltage divider using two resistors ( 10kΩ, 14kΩ) and a Z-Diode (5,1V)

-> The Z-Diode protects the Arduino in case of overvoltage!

-> If we would like to measure the voltage up to 12V, we have to use simple maths calculation.

-> The maximum Voltage of the analog Port (A0) is 5V.

-> I made a small maths calculation. Have a look at this :D

You only have to modify the existing Circuit :D

Step 3: Loading the Code Onto Your Arduino:

If you created the circuit, load the following Arduino Code onto your Microcontroller.

-> Have fun with your new car battery measurement system :D

-> Please contact me, if you have any problems :D

Thank you very much

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    9 Discussions


    1 year ago

    I really enjoyed reading through this 'able!

    You say "Please do not measure higher voltage than 12V!"

    But a fully charged car battery is about 12.6V. 13V still isn't really an acceptable maximum either, 14.4 is what I've got with my car idling, And i say this because I don't think there are many arduino tinkerers without a voltmeter. So IMO this application would be best as 'build and implant into your car' where you could print the output to an LCD or send it through bluetooth.

    And you're so very close to meeting the 10-15V range, You could easily if, you again apply yourself.


    2 years ago

    Hey, I Like this topic alot. I Would like to add LED to blink when voltage is getting low. Is this possible? Could somebody set me in the right direction. Thx Cheers


    4 years ago on Introduction

    You should try and modify it to read greater than 12v. A car battery usually sits between 12.4 and 12.7 but can get almost to 14 when the car is idling and the alternator is charging the battery.

    4 replies

    Reply 4 years ago

    hey mrandle:) ok you are right will update it as soon as I can.

    Timofte Andreimrandle

    Reply 4 years ago on Introduction

    make the voltage divider for 15V to 5V! the zener diode might provide some sort of protection but you'll be out of scale if you're measuring higher voltages... Don't forget about voltage spikes!


    Reply 4 years ago on Introduction

    Thank you very much :) If you want to know, how to measure higher voltages, dont be afraid to ask me :D