Hello,

Information: The original project code, written in C, has been translated and adapted for the Arduino / Arduino Nano environment. This version is based on the battery analyzer project and has been modified to work with the Arduino Nano and the ATmega328P microcontroller.

This project is an Arduino-based battery analyzer designed to measure battery capacity, estimate internal resistance, and operate as a constant-current electronic load. It can be used not only with single 18650 Li-ion cells, but also with other rechargeable batteries and battery packs up to approximately 20 V.

Functions

• Power supply requirement: 12 V, 250 mA
• Input voltage: 0.8–20 V, measurement resolution 0.01 V
• Adaptable for other batteries or battery packs up to approximately 20 V
• Battery capacity measurement
• Constant-current load operation
• Internal resistance measurement
• Discharge current: 0.01–2.55 A
• Control interface: 4 push buttons and a 20x4 character LCD
• Optional fan control using an LM35 temperature sensor

LCD Menu and Measurement Screens

The project uses a 20x4 character LCD for menu navigation, capacity measurement, constant-current load testing, internal resistance measurement, and device settings.

Main Menu

Capacity Measurement

This mode is used to discharge the connected battery at the selected current and calculate the measured capacity.

Constant-Current Mode

This mode allows the circuit to operate as a constant-current electronic load.

Internal Resistance Measurement

This mode estimates the internal resistance of the battery by comparing voltage values under different load-current conditions.

Settings Menu

The settings menu includes options such as sound control, ADC offset compensation, and saving calibration values to EEPROM.

Hardware

• Arduino Nano / ATmega328P
• Battery holder or external terminals for battery connection
• Load resistors
• MOSFET driver/control stage
• LCD display
• Voltage divider for voltage measurement
• Current measurement circuit
• Cooling fan for the load resistors and MOSFET

Schematic

The schematic below shows the connections for the Arduino Nano, LCD interface, voltage divider, MOSFET-based load stage, current measurement section, buzzer, fan output, and power supply regulators.

PCB Layout

The PCB layout includes the Arduino Nano, LCD connector, MOSFET load section, load resistor bank, voltage measurement input, current measurement path, fan output, and power supply section.

Important Note

This project is intended for educational and testing purposes only. When working with Li-ion batteries, lead-acid batteries, NiMH packs, or other rechargeable batteries, proper precautions must be taken due to the risks of short circuits, excessive current, reverse polarity, overheating, and incorrect voltage-divider calibration.

For battery voltages higher than a single Li-ion cell, the voltage divider ratio, load resistor power rating, MOSFET voltage and current ratings, heat dissipation, and software calibration values must be checked and adjusted accordingly before use.

The maximum usable battery voltage depends on the voltage divider ratio, ADC input limits, MOSFET specifications, load resistor power rating, fuse value, PCB trace current capacity, and cooling performance.

Related article / project page:

https://320volt.com/arduino-pil-analizoru/

GitHub

https://github.com/gevv/arduino-battery-analyzer/

Original project:

https://tefatronix.g6.cz/display.php?page=batmeter