How to Build a Simple Arduino Battery Monitor for $5

Introduction

Building a battery monitor with Arduino is an easy and inexpensive way to keep tabs on your battery's voltage level. With just a few components, you can assemble a simple circuit on a breadboard that will accurately read and display the voltage of a battery. This project is beginner-friendly and can be built in under an hour for around $5!

In this guide, I will walk you through the process of building a basic Arduino battery monitor, including:

• The parts and tools you'll need
• The circuit diagram and connections
• The code to measure and display voltage
• Calibration and usage instructions
• Tips for expanding the project

With just a little bit of time and a few common components, you'll have your own Arduino voltage monitor up and running in no time!

Parts and Tools Needed

To build the Arduino battery monitor, you will need the following parts and tools:

Parts

• Arduino Uno or compatible board
• Breadboard
• Jumper wires
• 10k ohm resistor
• Zener diode, 3.3V or 5.1V
• 16x2 LCD display module
• 10k potentiometer
• Battery pack or power source to monitor

Tools

• Solderless breadboard
• Jumper wires
• Arduino IDE (installed on computer)
• USB cable

Most of these components are very inexpensive and can be purchased online or at your local electronics store. The total cost should be around $5 depending on what parts you already have on hand.

Circuit Diagram and Connections

The circuit for the Arduino battery monitor only requires connecting six components together, not counting the battery pack. Here is the circuit diagram:

And here is how to connect each part:

• Connect the 10k ohm resistor from Arduino's A0 pin to the positive terminal of the battery pack.
• Connect the zener diode in parallel with the battery pack's positive and ground terminals. Make sure to orient the diode correctly.
• Connect the LCD display module to Arduino using jumper wires. See pinout diagram on LCD for specifics.
• Connect the 10k potentiometer to Arduino's A1 pin. This is used to adjust contrast on the LCD.
• Connect the battery pack's ground to Arduino's ground pin.

Be sure to connect the components correctly to avoid any issues. The resistor and diode act as a voltage divider to step down the battery voltage to a readable level for the Arduino's analog input.

Arduino Code

The Arduino sketch (code) to measure and display the battery voltage is fairly simple. Here are the key parts:

• Include the LiquidCrystal library to control the LCD
• Set up constants for the LCD pins and column count
• Read the analog voltage on pin A0 and convert to actual voltage based on resistor ratios
• Display the voltage on the LCD
• Add a short delay before repeating

The full code can be found in the link below:

Arduino Battery Monitor Code

This code can simply be uploaded to the Arduino after installing the LCD and LiquidCrystal libraries.

Calibrating the Monitor

Before relying on the voltage measurements from the monitor, it's a good idea to calibrate it for accuracy. Here's how:

• Apply a known voltage source to the input, such as a high-quality benchtop power supply.
• Adjust the potentiometer until the LCD display matches the expected voltage.
• Repeat for at least two voltage points across the expected range.
• Check linearity and adjust code resistor ratios as needed.

Taking the time to calibrate will ensure you get reliable and accurate results from your Arduino battery monitor. Expect accuracy within about 5% of the actual voltage.

Using the Battery Monitor

Once assembled, calibrated, and programmed, using the Arduino battery monitor is as simple as connecting a battery and reading the voltage on the LCD display!

Some usage tips:

• Use jumper wires to connect to batteries that do not have screw terminals.
• Monitor voltage over time to detect when batteries need recharging.
• Compare voltages of batteries before connecting them in series or parallel.
• Add a piezo buzzer to sound an alarm when voltage drops too low.

With this cheap and easy to build monitor, you'll always know the state of your batteries!

Going Further

Here are some ideas for enhancing and expanding the capabilities of the basic Arduino battery monitor:

• Add a numeric keypad to enter calibration points precisely
• Install monitor in a protective enclosure with charging/discharging ports
• Log voltage data to a microSD card for tracking over time
• Connect via Bluetooth or WiFi to remotely monitor voltages
• Interface with solar panels, motors, or other devices to measure power budgets
• Switch from LCD to OLED graphical display for flexibility

By leveraging the Arduino platform, you can create an increasingly complex and feature-rich battery monitoring solution. The possibilities are endless!

Conclusion

Building your own Arduino-based battery monitor is a simple weekend project that can give you valuable insights into your battery health and usage. With just $5 worth of common components, you can assemble a basic yet functional voltmeter that works with any battery.

Use this guide to understand the parts required, connections needed, Arduino code, calibration, and usage tips. And consider the many options for enhancing your monitor as you gain experience. With DIY Arduino projects like this, you'll be able to create customized, professional-grade devices on a budget!