Arduino LiPo Battery Watcher

Introduction: Arduino LiPo Battery Watcher

About: After reading this, you won't be more clever then before!

With the Help of 2 Arduinos, too low LiPo Batteries will never be a problem again.

I made this project for this particular reason:

Many people can't view their LiPo-Battery-Volatage, bacause their Radio for the RC-Stuff hasn't got telemetry or can't handle such high voltages.

Step 1: Let's Connect the Speaker to Your Receiver.

First, connect some piezoelectric speaker to your Arduino, in my case it's an Arduino UNO.

- > GND

+ > Any PWM Pin you like, be careful when programming.

Step 2: Connect the 433 MHz Receiver-Module to Your Arduino.

Be sure to connect the DATA-Pin to Pin #2, that's Interrupt #0 on your Arduino UNO.


VCC > 5v

DATA > Pin 2

Most Receiver-Units today come with only 4 Pins, unlike in the picture.

Connect these the same way as above.

Step 3: Connect the 433 MHz Transmitter-Module to Your Transmitting Arduino.


VCC > 5v

DATA > Any pin you like, be careful to choose the right pin when programming.

Step 4: Connect 2 Wires to Your Transmitting Arduino.

The first wire goes from the GND Pin of your Arduino to the Ground of the balancer-Connection on your LiPo-Battery.

The second one goes from any Analog Input Pin of your Arduino to the first cell on your balancer-port on your LiPo-Battery.

DO NOT connect this wire to any other cell on your LiPo-Battery then to the first one!

Step 5: Give the Transmitting Arduino Some Power.

Because the voltage-regulator on the original Arduino MICRO isn't the best one you can get, the Arduino MICRO will read some wrong values out of your LiPo-Battery.

Therefore, the Arduino MICRO gets it's power from an external, 5 Volt UBEC.

If you're a bit into that kind of RC-Stuff, you will know what a UBEC is.

If not, just google it.

Basically, it's a power regulator that converts, for example, 5 - 20 Volts to constantly 5v.

+ 5v from UBEC > +5v on your Arduino MICRO

- from UBEC > GND on your Arduino MICRO

When you're using an Arduino UNO, you can connect voltages anywhere between 7 - max. 20 Volts directly on your Vin Pin on your Arduino UNO.

Ground goes to GND.

Step 6: Add Coil Loaded Antennas to Your 433 RF-Modules.

The Antenna should look like in the images above.

Solder them onto the ANT-Connection directly to the PCB of the RF-Modules.

You will notice. that you'll get WAAAAY more range out of these small electronic parts!

Do the same thing on both your transmitter and your receiver modules.

Step 7: Give the Receiving Arduino Something to Eat

Take a battery, 7 - max. 20 Volts, and connect it to your Arduino UNO.

+ of your battery > Vin Pin on Arduino UNO

- of your battery > GND on your Arduino UNO

A switch probably wouldn't be bad, either... ;)

Step 8: Program the Transmitter.

You can find the scetch on

Step 9: Program the Receiver-unit.

You can find the sketch on

Step 10: Mount the Transmitter on Your RC-Stuff and Enjoy ;)

You have sucessfully build your LiPo-Watcher.

Now, you can take this one step further and add a LCD-Display, or all kind of stuff to it.

Don't forget to mount in onto your RC Multicopter/Plane/Car/Boat/...

In my case it's a Hexacopter.

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    5 years ago

    Great instructable! I understand you use this to avoid under-voltage while flying. If you also want to watch your battery under a tiny load, you might want to put a lot of emphasis on extreme low power usage and avoid a separate power supply, so actually self-measuring Vcc. Here is an example. Mind you, same idea, but different application.


    5 years ago

    Question about Sender:
    You make 4 Measurements and divide the result by 4 to get the average of the values. But what is dividing by 197.0 or any other value for. Btw, nice instructable


    Reply 5 years ago

    Hi @Raffi120,

    Thank you for your comment.

    It's a short answer:

    Let's say, You have a LiPo-battery that's fully charged @4.2v.
    In your code, remove the " / 197.0", so the Arduino won't divide through anything.
    Connect your battery to the Arduino, power it, and have a look on your serial monitor.

    You will see, that the Arduino will display a number that equals ~827.4.

    BUT: 827.4 divided by 197.0 is 4.2.

    There you have it, your 4.2v that the Arduino should read!

    This is, because the Arduino on the analog input pins gives out

    0 when the voltage on the analog pin is 0v,

    1023 when the voltage on the analog pin is 5v.

    So, in order to get the voltage and not some "high" number, I divide it by 197.0.

    If your Arduino reads, for example, 3.8v, but the battery has 4.2v, just decrease the 197.0 to another value, until the Arduino reads the right voltage.


    Reply 5 years ago

    Thank you very much for your fast reply, your words sound logic absolutely!!!


    Reply 5 years ago

    Thank you for commenting, appriciate it!

    You're welcome!


    5 years ago

    Very nice!