Project Hub /Basic Analog & Power Electronics/Analog Amplifiers & Signal Conditioning/Build a Battery Internal Resistance Meter with Arduino and Atmel ATtiny85 IC

Intermediate

ARDUINO

₹500 – ₹1,500

3 – 6 Hours

Partial Kit

Build a Battery Internal Resistance Meter with Arduino and Atmel ATtiny85 IC

Learn how to build a custom battery internal resistance (ISR) meter using an ATtiny85 microcontroller, LM358 op-amp, and an OLED display to accurately measure the internal resistance of various cells.

Originally published on CircuitDigest

View original tutorial

Parts You'll Need

This project is sourced from another site, not written by us — this list is our best match of their components against what we stock, not a verified bill of materials. Always check the original blog (linked above) for the actual parts list before buying.

10pcs - 220 ohm 1/4 W Resistor Set Rs. 39.00
2-Slot 18650 Holder with Protective Cover and On/Off Switch – Case Rs. 109.00
0.96 Inch I2C/IIC 4pin OLED Display Module White Rs. 349.00
400 Points Mini Solderless Prototype PCB Breadboard High Quality Rs. 89.00
MB102 Adjustable Breadboard Power Supply Module (3.3V & 5V) for Arduino & Raspberry Pi Rs. 139.00
Jumper Wire 10 Pin Male To Male 20cm Rs. 45.00
Jumper Wire 10 Pin Male To Female 20cm Rs. 45.00

Selected: Rs. 0.00

This list includes a generic resistor set as a placeholder — it is not matched to the exact value or part number this circuit needs. The correct one is specified on the original source page linked above; check it before buying.

We don't carry yet: ATtiny
LM35 / Analog Temp Sensor
Transistors (BC547 / 2N2222 / TIP / MOSFET)
AA / AAA Battery + Holder
Capacitors
Custom PCB / PCB Fab

Browse all components

How It Works

This DIY battery internal resistance meter operates by applying a controlled electrical load to a battery and measuring the resulting voltage drop. The core of the circuit is managed by an Arduino Uno or an ATtiny85 microcontroller, which controls a low VGS MOSFET using a push-button trigger. When activated, the MOSFET switches a known 1R resistor load across the battery terminals, drawing a temporary current. Because every real battery has internal resistance, placing a load on it causes its terminal voltage to drop proportionally. The tiny voltage changes across the circuit are too small for the microcontroller to read directly, so an LM358 operational amplifier is used in a signal conditioning configuration to amplify these analog voltage differences. A 0.1uF capacitor helps stabilize power supply noise during switching, while standard 1K resistors assist in biasing and signal routing. Once the amplified voltage values under loaded and unloaded conditions are sampled by the microcontroller's analog-to-digital converter, the internal resistance is calculated using Ohm's Law. Finally, the calculated internal resistance value is transmitted to a compact 128X64 OLED Module via an I2C or similar digital protocol, allowing the user to instantly read the health of the battery right on the custom PCB screen powered through the integrated battery holder.

Why Build This

Quickly test the health and remaining lifespan of rechargeable lithium-ion cells before using them in school or hobbyist electronics projects.

Add a custom, highly useful piece of test bench instrumentation to your electronics workstation without buying expensive commercial equipment.

Gain practical experience designing and building analog-digital hybrid circuits combining microcontrollers, op-amps, and display modules.

Real-World Application

Testing battery health, health assessment of rechargeable lithium-ion cells, and DIY electronics test bench instrumentation.

Skills You'll Learn

Operational amplifier signal conditioning

analog-to-digital conversion

MOSFET load switching

OLED display interfacing

custom PCB assembly

basic power electronics measurement

Safety Precautions

Be cautious when handling high-current lithium cells and avoid short-circuiting battery terminals.

Technology Tags

ATTINY85

ARDUINO

OLED DISPLAY

MOSFET

LM358 OP-AMP

PCB DESIGN

EAGLE

VOLTAGE DIVIDER

BATTERY TESTING

Frequently Asked Questions

Why is an op-amp like the LM358 needed instead of just connecting the battery directly to the microcontroller?

The voltage drop caused by measuring internal resistance is often very small. The LM358 op-amp amplifies this tiny analog signal so that the ATtiny85 or Arduino can read the difference accurately.

Can I power this meter using the same battery I am trying to test?

Yes, the circuit is designed to be flexible, but ensuring a stable power supply through the battery holder is important so the microcontroller and OLED module do not reset during high-current load pulses.

What is the purpose of the low VGS MOSFET and the 1R resistor?

The low VGS MOSFET acts as an electronic switch controlled by the microcontroller, quickly applying the 1R load resistor across the battery to safely create the current draw needed for the resistance calculation.

Gallery

This page is part of Kitkraft's Project Hub — a curated collection of electronics & robotics projects gathered from the maker community to help students and hobbyists discover and learn to build. Kitkraft does not claim authorship of the original project, and makes no representation as to the accuracy, completeness or safety of third-party source material. The summary and "How It Works" explanation above are AI-generated, rewritten with reference to the original tutorial — not a reproduction of it. Full credit and a direct link to the original source are provided above. If you're the original creator and have a concern about how your work is represented here, please contact us and we'll address it promptly.

Kitkraft Project Hub — curated from the maker community, credited at the source.

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