How to Use INR21700: Examples, Pinouts, and Specs

The Samsung INR21700 is a high-performance lithium-ion rechargeable battery cell designed for demanding applications. With its cylindrical 21700 form factor, it offers a nominal voltage of 3.7V and is known for its high energy density, long cycle life, and excellent thermal stability. These characteristics make it a popular choice for applications such as electric vehicles (EVs), power tools, energy storage systems, and portable electronics.

• Electric Vehicles (EVs): Used in battery packs for extended driving range.
• Power Tools: Provides reliable power for cordless drills, saws, and other tools.
• Energy Storage Systems: Ideal for renewable energy storage solutions.
• Portable Electronics: Powers devices like laptops, flashlights, and drones.

Below are the key technical details of the Samsung INR21700 battery cell:

The INR21700 is a cylindrical cell with two terminals:

1. Battery Holder or Spot Welding: Use a compatible 21700 battery holder or spot-weld nickel strips to the terminals for secure connections.
2. Charging: Use a lithium-ion battery charger with a constant current/constant voltage (CC/CV) profile. Ensure the charging voltage does not exceed 4.2V.
3. Discharging: Connect the battery to your load, ensuring the current draw does not exceed the maximum discharge current (15A–35A, depending on the model).
4. Protection Circuit Module (PCM): Always use a PCM or Battery Management System (BMS) to prevent overcharging, over-discharging, and short circuits.

• Thermal Management: Ensure proper ventilation or cooling to prevent overheating during high-current discharge.
• Storage: Store the battery in a cool, dry place at a charge level of 40–60% for long-term storage.
• Safety Precautions: Avoid puncturing, short-circuiting, or exposing the battery to fire or water.
• Series/Parallel Connections: When connecting multiple cells, ensure they are balanced and use a BMS to manage the pack.

To power an Arduino UNO with an INR21700, you can use a DC-DC step-down converter to regulate the battery's voltage to 5V. Below is an example circuit and code:

1. Connect the positive terminal of the INR21700 to the input of the DC-DC converter.
2. Connect the output of the DC-DC converter to the Arduino UNO's 5V and GND pins.
3. Use a BMS to protect the battery during operation.

// Example code to blink an LED using Arduino UNO powered by INR21700
// Ensure the DC-DC converter outputs a stable 5V to the Arduino

const int ledPin = 13; // Pin connected to the onboard LED

void setup() {
  pinMode(ledPin, OUTPUT); // Set the LED pin as an output
}

void loop() {
  digitalWrite(ledPin, HIGH); // Turn the LED on
  delay(1000);                // Wait for 1 second
  digitalWrite(ledPin, LOW);  // Turn the LED off
  delay(1000);                // Wait for 1 second
}

1. Battery Overheating:

   • Cause: High discharge current or poor ventilation.
   • Solution: Reduce the load current and ensure proper cooling.

2. Battery Not Charging:

   • Cause: Faulty charger or damaged battery.
   • Solution: Check the charger output voltage and replace the battery if necessary.

3. Short Cycle Life:

   • Cause: Frequent deep discharges or overcharging.
   • Solution: Use a BMS and avoid discharging below 2.5V or charging above 4.2V.

4. Voltage Drop Under Load:

   • Cause: High internal resistance or excessive current draw.
   • Solution: Use a battery with a higher discharge rating or reduce the load.

Q: Can I use the INR21700 without a BMS?
A: It is not recommended. A BMS ensures safe operation by preventing overcharging, over-discharging, and short circuits.

Q: How do I dispose of an INR21700 battery?
A: Dispose of the battery at a certified recycling facility. Do not throw it in regular trash.

Q: Can I connect multiple INR21700 cells in series or parallel?
A: Yes, but ensure the cells are balanced and use a BMS to manage the pack safely.

Q: What is the self-discharge rate of the INR21700?
A: The self-discharge rate is typically very low, around 2–3% per month under normal conditions.