How to Use 12.6V 3S 20A 18650 BMS Protection Board Module: Examples, Pinouts, and Specs

The 12.6V 3S 20A 18650 BMS Protection Board Module is a Battery Management System (BMS) designed for 3-cell (3S) lithium-ion battery packs. It ensures the safe operation of lithium-ion batteries by providing essential protections, including overcharge, over-discharge, overcurrent, and short-circuit protection. This module is ideal for applications requiring reliable battery management, such as power banks, electric bicycles, solar energy systems, and other portable electronic devices.

• Power banks and portable chargers
• Electric bicycles and scooters
• Solar energy storage systems
• DIY battery packs for robotics and IoT devices
• Backup power supplies and uninterruptible power systems (UPS)

The following table outlines the key technical details of the 12.6V 3S 20A 18650 BMS Protection Board Module:

The module has several connection points for proper integration into a circuit. The table below describes each pin:

1. Wiring the Battery Pack:

   • Connect the negative terminal of the battery pack to the B- pin.
   • Connect the positive terminal of the first cell to the B1 pin.
   • Connect the positive terminal of the second cell to the B2 pin.
   • Connect the positive terminal of the battery pack to the B+ pin.

2. Connecting the Load and Charger:

   • Connect the negative terminal of the load or charger to the P- pin.
   • Connect the positive terminal of the load or charger to the P+ pin.

3. Verify Connections:

   • Double-check all connections to ensure proper polarity and avoid short circuits.
   • Ensure the battery pack is balanced and within the voltage range of the module.

4. Power On:

   • Once all connections are secure, the module will automatically manage the battery pack, providing protection and balancing.

• Battery Matching: Use cells with the same capacity, voltage, and internal resistance to ensure proper operation.
• Heat Dissipation: Ensure adequate ventilation or heat sinking if the module operates near its maximum current rating.
• Avoid Overloading: Do not exceed the 20A maximum continuous current rating to prevent damage to the module.
• Balancing: The module includes a balancing function to equalize the voltage of each cell, improving battery life and performance.

If you are using the BMS module to power an Arduino UNO, ensure the output voltage of the battery pack (8.4V to 12.6V) is within the Arduino's input voltage range. Use the following code to monitor the battery voltage via an analog pin:

// Arduino code to monitor battery voltage using an analog pin
const int batteryPin = A0; // Analog pin connected to battery output
float voltageDividerRatio = 5.7; // Adjust based on resistor values in voltage divider
float referenceVoltage = 5.0; // Arduino reference voltage (5V for most boards)

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

void loop() {
  int analogValue = analogRead(batteryPin); // Read analog value from battery
  float batteryVoltage = (analogValue / 1023.0) * referenceVoltage * 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
}

Note: Use a voltage divider circuit to step down the battery voltage to a safe level for the Arduino's analog input pin.

1. Module Overheating:

   • Cause: Exceeding the maximum current rating or poor ventilation.
   • Solution: Reduce the load current or improve heat dissipation with a heatsink or fan.

2. Battery Pack Not Charging:

   • Cause: Incorrect wiring or damaged cells.
   • Solution: Verify all connections and check the battery pack for faulty cells.

3. Uneven Cell Voltages:

   • Cause: Cells with mismatched capacities or internal resistances.
   • Solution: Replace mismatched cells and allow the module's balancing function to equalize the voltages.

4. Short-circuit Protection Triggered:

   • Cause: Accidental short circuit or excessive load.
   • Solution: Disconnect the load, check for wiring issues, and reconnect after resolving the problem.

• Q: Can this module be used with a 4S battery pack?
  A: No, this module is specifically designed for 3S (3-cell) battery packs. Using it with a 4S pack may result in improper operation or damage.

• Q: Does the module support lithium iron phosphate (LiFePO4) batteries?
  A: No, this module is optimized for lithium-ion batteries. LiFePO4 batteries have different voltage thresholds and require a dedicated BMS.

• Q: How do I know if the balancing function is working?
  A: The balancing function operates automatically when cell voltages differ. You can measure individual cell voltages to confirm balancing activity.

• Q: Can I use this module for charging and discharging simultaneously?
  A: Yes, the module supports simultaneous charging and discharging, provided the connections are correct and the current limits are not exceeded.