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.