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How to Use 18650 7.4V 2S Li-ion Battery: Examples, Pinouts, and Specs

Image of 18650 7.4V 2S Li-ion BatteryDesign with 18650 7.4V 2S Li-ion Battery in Cirkit Designer

Introduction

The 18650 7.4V 2S Li-ion Battery, manufactured by Espressif, is a rechargeable lithium-ion battery pack composed of two 18650 cells connected in series. This configuration provides a nominal voltage of 7.4V and is widely recognized for its high energy density, long cycle life, and reliability. It is an ideal power source for a variety of applications, including portable electronics, robotics, electric vehicles, and backup power systems.

Explore Projects Built with 18650 7.4V 2S Li-ion Battery

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Image of Battery-Powered 18650 Li-ion Charger with USB Output and Adjustable Voltage Regulator: A project utilizing 18650 7.4V 2S Li-ion Battery in a practical application
Battery-Powered 18650 Li-ion Charger with USB Output and Adjustable Voltage Regulator

This circuit is a battery management and power supply system that uses three 3.7V batteries connected to a 3S 10A Li-ion 18650 Charger Protection Board Module for balanced charging and protection. The system includes a TP4056 Battery Charging Protection Module for additional charging safety, a Step Up Boost Power Converter to regulate and boost the voltage, and a USB regulator to provide a stable 5V output, controlled by a push switch.

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Common Applications

Technical Specifications

The following table outlines the key technical details of the 18650 7.4V 2S Li-ion Battery:

Parameter Specification
Nominal Voltage 7.4V
Capacity Range 2000mAh to 3500mAh (varies by model)
Maximum Charging Voltage 8.4V
Discharge Cutoff Voltage 6.0V
Maximum Continuous Current 2A to 10A (depending on cell type)
Chemistry Lithium-ion
Configuration 2S (two cells in series)
Cycle Life 300–500 cycles (typical)
Operating Temperature -20°C to 60°C
Dimensions Varies based on cell holder design
Weight ~90g to 120g (depending on capacity)

Pin Configuration and Descriptions

The 18650 7.4V 2S Li-ion Battery typically has three terminals: Positive (+), Negative (-), and a Battery Management System (BMS) connection for protection. The table below describes the pin configuration:

Pin Label Description
1 + Positive terminal of the battery pack. Connect to the positive side of the load.
2 - Negative terminal of the battery pack. Connect to the negative side of the load.
3 BMS Connection to the Battery Management System for overcharge and discharge protection.

Usage Instructions

How to Use the Component in a Circuit

  1. Connection: Connect the positive terminal (+) of the battery to the positive input of your circuit and the negative terminal (-) to the ground or negative input.
  2. Charging: Use a compatible Li-ion battery charger designed for 2S (7.4V) configurations. Ensure the charger has overcharge protection and does not exceed 8.4V.
  3. Load Compatibility: Verify that the load does not exceed the battery's maximum continuous current rating. For high-current applications, ensure proper heat dissipation.
  4. Protection Circuit: Always use a Battery Management System (BMS) to prevent overcharging, over-discharging, and short circuits.

Important Considerations and Best Practices

Example: Using with Arduino UNO

The 18650 7.4V 2S Li-ion Battery can be used to power an Arduino UNO via its VIN pin. Below is an example circuit and code to read the battery voltage using a voltage divider:

Circuit Setup

  1. Connect the battery's positive terminal to the VIN pin of the Arduino UNO.
  2. Connect the battery's negative terminal to the GND pin of the Arduino UNO.
  3. Use a voltage divider (e.g., 10kΩ and 20kΩ resistors) to step down the battery voltage for safe measurement by the Arduino's analog input pin.

Arduino Code

// Define the analog pin connected to the voltage divider
const int voltagePin = A0;

// Define the voltage divider ratio (e.g., 10kΩ and 20kΩ resistors)
const float voltageDividerRatio = 3.0;

// Reference voltage of the Arduino (5V for most boards)
const float referenceVoltage = 5.0;

void setup() {
  Serial.begin(9600); // Initialize serial communication
}

void loop() {
  // Read the analog value from the voltage divider
  int analogValue = analogRead(voltagePin);

  // Convert the analog value to the actual battery voltage
  float batteryVoltage = (analogValue * referenceVoltage / 1023.0) * voltageDividerRatio;

  // Print the battery voltage to the Serial Monitor
  Serial.print("Battery Voltage: ");
  Serial.print(batteryVoltage);
  Serial.println(" V");

  delay(1000); // Wait for 1 second before the next reading
}

Troubleshooting and FAQs

Common Issues and Solutions

  1. Battery Not Charging

    • Cause: Faulty charger or damaged BMS.
    • Solution: Verify the charger output voltage and current. Replace the charger or BMS if necessary.

  2. Battery Drains Quickly

    • Cause: High self-discharge rate or excessive load.
    • Solution: Check for parasitic loads in the circuit. Replace the battery if it has degraded.

  3. Overheating During Use

    • Cause: Excessive current draw or poor ventilation.
    • Solution: Ensure the load is within the battery's current rating. Improve heat dissipation.

  4. Voltage Drops Below 6.0V

    • Cause: Over-discharge due to lack of BMS.
    • Solution: Use a BMS to prevent over-discharge. Recharge the battery immediately.

FAQs